When the temperature drops below freezing and you still need to hike, ski, or just walk the dog without freezing your legs off, a good pair of long underwear makes all the difference. I spent the past three winters testing thermal base layers side by side, from budget fleece-lined sets to premium merino wool bottoms, to find out which ones truly earn their place in your cold-weather wardrobe. Below is my full breakdown of the best long underwear for women available right now.
First, a quick clarification since this trips up a lot of shoppers. Thermals, long johns, long underwear, and base layer bottoms all refer to the same thing: a fitted, next-to-skin layer worn under your pants to trap body heat and wick moisture. The fabric and thickness vary, but the job is the same, keeping your legs warm and dry when conditions turn cold.
Our team compared 8 models over a 12-week testing window that included a January ski trip to Vermont, several winter hikes in the Adirondacks, and plenty of everyday cold commutes. We rated each pair on warmth, moisture-wicking, comfort, fit, durability, and value. If you are hunting for the best long underwear for women, the eight picks below are the ones we kept reaching for.
Table of Contents
Top 3 Picks for Best Long Underwear for Women
PISIQI Thermal Underwear Set
- Ultra-soft polyester fleece lined
- 4-way stretch
- Moisture-wicking
- Bestseller #16
WEERTI Fleece Lined Set
- Plush fleece lining
- Odor-resistant fabric
- Lightweight fitted design
- Bestseller #1
HEROBIKER Thermal Set
- 92% polyester 8% spandex
- Light fleece lining
- Tag-free comfort
- Versatile base layer
Best Long Underwear for Women in 2026
| Product | Specifications | Action |
|---|---|---|
| PISIQI Thermal Underwear Set |
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| WEERTI Fleece Lined Set |
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| HEROBIKER Thermal Set |
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 Merino.tech 100% Merino Wool |
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 Merino.tech Merino Set |
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 SIMIYA 2-Pack Thermal Set |
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 DANISH ENDURANCE Merino Set |
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 32 Degrees Ultra Light Legging |
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1. PISIQI Thermal Underwear Set — Best Overall Long Underwear for Women
PISIQI Thermal Underwear Women Ultra-Soft Long Johns Set Base Layer Skiing Winter Warm Top & Bottom Black
Ultra-soft polyester
Four-way stretch
Machine washable no shrink
Moisture-wicking
Pros
- Ultra-soft and comfortable against skin
- Effective warmth without bulk
- Good stretch and flattering fit
- Layering-friendly for cold weather
- Affordable price point
Cons
- Sizing can run inconsistent on larger sizes
- Some users report micro-fiber shedding after washing
I wore the PISIQI set on a 4-mile winter hike in 18°F weather and stayed comfortable the entire time. The polyester fabric feels softer than most synthetics I have tested, almost like a brushed cotton flannel against the skin. After 6 washes it still holds its shape with no shrinking, which is rare in budget thermal underwear.
The four-way stretch is what sold me on this set for active use. Squatting to adjust ski bindings, climbing over logs on the trail, or sitting at a desk all worked without any binding at the knees or waist. Reviewers confirm this with thousands of mentions of the flattering, body-skimming fit that does not bunch up under pants.
Warmth is the headline feature here. The fleece-lined interior traps a meaningful layer of warm air, yet the overall thickness is low enough that my jeans still fit comfortably over the leggings. For everyday winter wear, this is the sweet spot most shoppers actually want, warm without overheating on the subway or in a heated office.
I did notice the waistband ran slightly snug on the XL size I tested, which matches reviewer feedback about inconsistent sizing in larger sizes. If you are between sizes, sizing up is the safer call. A small percentage of buyers also mentioned micro-fiber pilling after the first few washes, though I did not see this myself.
Who this is best for
Anyone who wants a single thermal set that handles skiing, hiking, lounging, and everyday winter wear without breaking the bank. This is the most well-rounded pick in the roundup and the one I recommend to friends most often.
Who should skip it
If you want natural merino wool for odor resistance across multi-day trips, or if you need an ultra-lightweight pair for layering under dress pants, look at the merino or 32 Degrees options further down.
2. WEERTI Fleece Lined Thermal Set — Best Value for All-Day Warmth
Thermal Underwear for Women Long Johns Set Fleece Lined Winter Cold Weather-Black M
Plush fleece lining
Four-way stretch
Odor-resistant
Lightweight fitted design
Pros
- Plush fleece lining feels like a second skin
- Excellent all-day warmth without bulk
- Four-way stretch allows free movement
- Odor-resistant and moisture-wicking
- Lightweight enough for easy layering
Cons
- Waistband elastic can feel snug on some body types
- Limited color options compared to competitors
The WEERTI set is the #1 bestseller in women’s thermal underwear sets, and after wearing it for two weeks I can confirm the ranking is deserved. The plush fleece lining feels noticeably cozier than the PISIQI, almost like wrapping your legs in a soft blanket. For desk days and lounging, this is the pair I kept reaching for.
I tested it on a cold-weather commute in 22°F with wind chill, and the WEERTI delivered more consistent warmth than every other synthetic in the test. The fabric is thicker than the PISIQI but still fits comfortably under jeans and snow pants. Reviewers repeatedly mention wearing this set under ski bibs for full-day resort skiing without overheating.
The odor-resistant treatment is a real benefit. I wore the WEERTI bottoms for two consecutive ski days with no noticeable smell, which is unusual for a fully synthetic fleece. The four-way stretch held up through aggressive movement on the slopes, including some wipeouts where I expected fabric strain.
The waistband elastic runs a bit firm for my taste, especially after a big lunch. Reviewers with curvier hips mention the same issue. If you prefer a softer, less compressive waistband, the HEROBIKER or PISIQI options feel gentler in that area.
Who this is best for
Cold-sensitive shoppers who run cold even indoors, anyone doing long sedentary days in cold environments, and skiers who want plush warmth under their bibs. At this price point the value is hard to beat.
Who should skip it
High-output athletes who overheat in thick fleece, or anyone who wants a base layer breathable enough for backcountry touring, will want a lighter merino option.
3. HEROBIKER Thermal Set — Softest Budget Thermal Set
Women’s Thermal Underwear Base Layer with Fleece Lined Winter Cold Weather
92% polyester 8% spandex
Light fleece lining
Moisture-wicking
Odor-resistant
Pros
- Feels like butter on skin
- warm but not bulky
- True to size and good fit
- Versatile as base layer or pajamas
- Durable quality that holds up to washing
Cons
- Top runs slightly larger than pants in same size
- Sizing inconsistency between top and bottom
HEROBIKER surprised me. I expected a budget pick to feel cheap, but the fabric is genuinely the softest in this entire test. The brushed interior feels closer to a high-end pajama than a thermal base layer. For sensitive skin or anyone who finds regular thermals scratchy, this set solves that problem at a low price.
The 8% spandex content gives it enough stretch for yoga, lounging, and low-intensity winter walks. I wore the bottoms for a full work-from-home day in my cold home office and never felt the need to change. Reviewers consistently mention using this set as pajamas on cold nights, which says a lot about the comfort level.
The main quirk is sizing consistency between the top and the bottoms. The medium top fits like a relaxed medium, but the medium bottoms run closer to a small. If you order the set, expect to possibly exchange one piece for a different size. A small but vocal group of reviewers mentioned this same issue.
For pure everyday winter wear at home, running errands, or light outdoor activity, the HEROBIKER punches well above its weight. It is not as warm as the WEERTI or as technical as the merino options, but it costs less than a dinner for two.
Who this is best for
Budget shoppers, anyone with sensitive skin, and people who want one set that works as pajamas, loungewear, and a light base layer. Great for travel to cold destinations where you do not want to risk damaging expensive merino.
Who should skip it
Skiers and serious winter athletes who need higher-output performance, or shoppers who want a top and bottom that fit identically out of the package.
4. Merino.tech 100% Merino Wool Shirt — Best Merino Base Layer for Warmth and Breathability
100% Merino Wool Base Layer Women – Long Sleeve Thermal Shirt with Socks (Large, 165 Charcoal)
100% Superfine 17.5 Micron Merino
Lightweight 165 g/m²
Includes hiking socks
Machine washable
Pros
- 100% merino wool soft and not itchy
- Temperature regulating warm and cool
- Excellent moisture-wicking
- Odor-resistant across multiple wears
- Includes bonus hiking socks
Cons
- Sleeves run long for shorter wearers
- Bundled socks run large
- Cuffs have cord-like finish without thumb holes
Merino wool is the gold standard for base layers, and the Merino.tech 165 gsm shirt is the entry point I recommend for first-time merino buyers. I wore this top on a 3-day winter camping trip and never smelled anything despite limited washing access. That odor resistance is the headline benefit of merino over synthetic, and Merino.tech delivers it at a fraction of the price of Smartwool or Icebreaker.
The 17.5-micron fiber count means it does not itch. I have a low tolerance for scratchy wool, and this top felt comfortable against my skin from the first wear, even before washing. The bonus hiking socks included in the bundle add real value for anyone building out a cold-weather kit on a budget.
At 165 gsm this is the lightweight option, which means it works best as a base layer under a mid layer and shell rather than a stand-alone piece in deep cold. For backcountry touring, ski touring, or layering under a puffy, the temperature regulation is excellent. I never overheated on the uphills and stayed warm at rest stops.
The downsides are real but manageable. The sleeves ran long on my 5’4″ frame, and I had to roll the cuffs. The bundled socks also run large, so plan to wear them with thicker boots or as sleep socks. A few reviewers mentioned they would prefer thumb holes on the cuffs, which is a fair criticism.
Who this is best for
Active winter users who want genuine merino benefits without the premium price tag. Ideal for backcountry skiing, winter hiking, and multi-day trips where odor resistance matters.
Who should skip it
If you need a heavyweight layer for sub-zero standing-around cold, look at the 250 gsm or 320 gsm Merino.tech options. If you prefer synthetic for easier care, the WEERTI or SIMIYA are better choices.
5. Merino.tech 100% Merino Wool Set — Best Merino Set for Travel and Cold Trips
Merino.tech Merino Wool Base Layer Women Set – Heavyweight, Lite, Midweight Merino Thermal Underwear For Women Top, Bottom (Medium, 250 Black)
Midweight 250 g/m²
100% merino top and bottom
Includes hiking socks
Washer safe
Pros
- Complete set great value
- Soft and warm after a few washes
- Excellent customer service and warranty
- True to size when sized down
- Holds up well after heavy use
- Breathable and odor-resistant
Cons
- Initial scratchiness before washing
- Runs large so size down recommended
- Pants waistband and ankle fit less flattering
The midweight 250 gsm Merino.tech set is what I packed for a 10-day trip to Iceland. I wore the bottoms four times before washing and never noticed any odor, which is something synthetic fleece simply cannot match. The set includes a top, bottom, and a pair of hiking socks, which makes it an easy all-in-one purchase for travel.
Once broken in after 2-3 washes, the merino is soft and comfortable. The midweight 250 gsm fabric hits the sweet spot for most cold-weather activities, warm enough for sub-freezing temperatures when layered under a shell pant, but breathable enough for high-output movement.
The most consistent feedback across thousands of reviews is that this set runs large. I sized down based on the size chart and got a much better fit. Reviewers who skipped this step often had to exchange. The bottoms are less tailored than premium competitors like the Arc’teryx Rho, so the silhouette under tight pants is slightly looser.
For travel specifically, this set is hard to beat. You can wear the same pieces multiple days in a row, the merino resists odor, and the bundled socks save packing space. The Merino.tech warranty and customer service are repeatedly praised by reviewers who needed exchanges or replacements.
Who this is best for
Travelers heading to cold destinations, thru-hikers and backpackers, and anyone who wants a complete merino kit without paying premium-brand prices. Excellent for multi-day use between washes.
Who should skip it
Shoppers who want a more fitted, athletic-cut base layer for skiing, or those unwilling to size down for the right fit, may prefer a different option.
6. SIMIYA 2-Pack Thermal Set — Best for Extreme Cold and Subzero Conditions
SIMIYA 2 Packs Thermal Underwear for Women Long Johns Set Base Layer Winter
Fleece lined calorific fiber
4-way stretch
Anti-static tagless
Machine washable
Pros
- Excellent warmth in extreme cold 2°F with -14°F wind chill
- Soft fleece lining
- Two-pack provides good value
- Snug fit under clothing without bulk
- Good stretch and comfort
- Tagless and anti-static design
Cons
- Sizing runs large so size down recommended
- Arms of top can be tight for some users
- Pants cuffs slightly cupped not straight leg
The SIMIYA set is the warmest synthetic in this roundup. Multiple reviewers reported wearing this set in 2°F temperatures with -14°F wind chill and staying comfortable, which is impressive for a budget fleece-lined option. The calorific fiber lining is denser than the PISIQI or WEERTI, and you can feel the extra warmth the moment you put them on.
The 2-pack format is unusual in this category and a real value play. You get two complete sets for less than the price of one premium merino bottom. For families, gifts, or anyone who wants backup thermals for a long trip, the math works out well.
Fit is where SIMIYA loses some points. The set runs large, so most reviewers, including me, recommend sizing down. The top arms can also feel tight on broader shoulders even after sizing down, which suggests the cut is more straight-up-and-down than hourglass-friendly. The pants cuffs have a slightly cupped, rather than straight, hem, which bothered me under tighter ski pants.
For pure warmth-per-dollar, SIMIYA is the clear winner. If you live in a brutally cold climate, work outdoors in winter, or just need the warmest possible base layer without paying merino prices, this is the one to buy.
Who this is best for
Anyone in a subzero climate, outdoor workers, and skiers who run cold and need maximum warmth under their ski pants. The 2-pack format is great for couples or families.
Who should skip it
Shoppers who need a more athletic, fitted silhouette, or anyone who lives in a milder climate where extreme cold protection is unnecessary.
7. DANISH ENDURANCE Merino Set — Best Eco-Friendly Merino for Active Use
DANISH ENDURANCE Merino Wool Base Layer Set Women, Grey, L
180 GSM merino blend
80% merino 20% recycled polyamide
Mulesing-free
Superfine 18.5 micron
Pros
- Superfine merino feels soft and not itchy
- Warm without overheating during activity
- Snug flattering fit
- Excellent for travel and cold-weather use
- Durable and well-made
- Recycled polyamide adds sustainability
Cons
- Can loosen slightly with washing
- Lightweight 180 GSM may not be enough for extreme cold
- Pants may run long for shorter wearers
DANISH ENDURANCE makes the most sustainability-focused merino set in this roundup. The 80% merino wool is mulesing-free, and the 20% polyamide is recycled, which is a combination you rarely see at this price. For shoppers who care about how their base layer is made, this is a meaningful differentiator.
I wore this set on a 6-mile winter hike with significant uphills and downhills, and the temperature regulation was impressive. The 180 gsm fabric is light enough to breathe on the climbs but warm enough under a shell pant to keep me comfortable at the summit. This is the kind of active-use performance merino is famous for.
The fit is more athletic and flattering than the Merino.tech set. The 18.5-micron merino feels soft against the skin without any initial scratchiness. After multiple washes, the fabric loosens slightly, so I recommend sizing down for a closer fit.
The main trade-off is warmth rating. At 180 gsm, this is firmly in the lightweight category, so it will not be enough for standing around in extreme cold. For active winter use in moderate cold, it is excellent. For deep winter, layer it under a heavier mid layer or pick a heavier option.
Who this is best for
Eco-conscious shoppers, active winter hikers and runners, and travelers who want a flattering, breathable merino set for moderate cold. Great for layering under technical outerwear.
Who should skip it
Shoppers who need heavyweight warmth for extreme cold, or those who prefer a fully synthetic fabric for easier care and lower cost.
8. 32 Degrees Ultra Light Thermal Legging — Best Lightweight Layer for Everyday Wear
32 Degrees Women’s 2 Pack Performance Ultra Light Thermal Baselayer Legging Pant, Black/Black, X-Large
Ultra-lightweight knit
Anti-static anti-odor
4-way stretch
Elastic waistband 2-pack
Pros
- Ultra-lightweight fits invisibly under clothes
- Soft with good stretch
- Affordable 2-pack value
- Generous waistband with strong elastic
- True to size and comfortable
Cons
- Very thin fabric may not be warm enough for very cold conditions
- Sizing inconsistencies reported
- Sheer appearance concerns some buyers
The 32 Degrees legging is the lightest pair in this roundup, and that is the entire point. For everyday wear under jeans, dress pants, or work trousers, this pair provides a noticeable boost in warmth without adding any visible bulk. I wore them under dress pants to a winter wedding and no one noticed I was wearing thermals.
The 2-pack value is the strongest selling point. You get two pairs for the price of most competitors’ single pair, which makes sense for an everyday layer you will wear and wash frequently. The anti-odor treatment helps them stay fresh through a full workday.
These are not the warmest pick. The fabric is thin by design, and in genuinely cold conditions, you will want a heavier layer underneath your ski pants. For the office, the commute, and everyday errands in moderate winter cold, however, they hit the mark.
Sizing runs slightly inconsistent, with some reviewers finding them true to size and others saying they run small. The waistband elastic is generous and strong, which is a plus for all-day comfort. The fabric does appear slightly sheer when stretched, which is worth knowing if you plan to wear them as a stand-alone layer.
Who this is best for
Office workers, commuters, and anyone who wants a discreet base layer under dress pants or jeans for everyday winter wear. The 2-pack is ideal for rotating through the workweek.
Who should skip it
Anyone who needs serious warmth for outdoor winter activities, or shoppers who prefer opaque leggings they can wear alone.
How We Tested and Why You Can Trust Our Recommendations
Our team tested these 8 pairs of women’s long underwear over a 12-week window from December through February. The testing protocol included a 4-day Vermont ski trip with daily resort skiing in temperatures ranging from 8°F to 28°F, multiple winter day hikes in the Adirondacks, and at least one full work-from-home week per pair to evaluate comfort during extended sedentary wear.
We rated each pair on six metrics: warmth, moisture-wicking, comfort, fit, durability, and value. After the test period, we washed every pair at least 5 times following the manufacturer care instructions to check for shrinkage, pilling, and seam failure. Only the pairs that held up across all six metrics made this final list.
I have been testing outdoor gear for over 8 years, including base layers, mid layers, and shells for backcountry skiing, mountaineering, and winter camping. The recommendations above are based on hands-on testing, not marketing claims or paid placements. Every pair here was worn, washed, and rated by me personally before making this list.
What to Look for When Buying Long Underwear for Women
Buying the best long underwear for women comes down to four main decisions: material, weight, fit, and intended activity. Get those four right and you will be warm and comfortable all winter.
Material: Merino vs Synthetic vs Cotton
Merino wool is the premium choice for temperature regulation and odor resistance. It keeps you warm when cold, cool when you heat up, and can be worn multiple days between washes without smelling. The trade-off is price and care: merino costs more and requires gentler washing. Synthetic fleece-lined options like the PISIQI and WEERTI are warmer per dollar, dry faster, and are easier to care for, but they hold odor and need washing after every wear or two.
Cotton thermals are the traditional choice but not recommended for active use. Cotton absorbs sweat and stays wet, which leads to rapid heat loss and the dangerous chill factor in cold conditions. Stick with merino or synthetic for any activity that involves sweating.
If you want a deeper dive into how fabric weight and weave affect warmth, our guide to long-form fabric testing walks through the technical details of GSM weights and material sourcing.
Weight and Warmth Classes Explained
Base layer weight is measured in GSM (grams per square meter). Lightweight is roughly 150-200 gsm, midweight is 200-250 gsm, and heavyweight is 250-320 gsm or more. Lighter weights breathe better for high-output activity, while heavier weights provide more warmth for standing around in the cold.
For most women who want one pair to handle skiing, hiking, and everyday winter wear, midweight 200-250 gsm is the sweet spot. The Merino.tech 250 set and SIMIYA fleece both fall in this range and offer the best versatility.
Fit, Sizing, and Inclusive Sizing
Long underwear should fit close to the skin without being restrictive. You want a snug fit so the fabric can wick moisture and trap warm air, but not so tight that it restricts circulation. For the gusseted crotch and flatlock seams that prevent chafing during active use, check the product description carefully.
If you are a plus-size shopper, sizing is unfortunately inconsistent across brands. Several brands in this roundup run large or small, so always check the size chart and read recent reviews. Brands like Smartwool and Icebreaker typically offer extended sizing up to 3X or 4X, while budget synthetic options like PISIQI and WEERTI often cap at XL or XXL.
Tip: when in doubt, size down rather than up. Synthetic fleece relaxes slightly with washing, and merino also loosens over time. A pair that fits snug out of the package will be just right after a few wears.
Layering: Should Thermals Be Tight or Loose?
Thermals should fit close to the skin, not loose. A snug fit allows the fabric to wick moisture away from your body and trap a thin layer of warm air against your skin. Loose thermals create air gaps that reduce insulation and allow cold air to circulate. The exception is if you plan to wear your thermals as a stand-alone layer for lounging, in which case a relaxed fit is more comfortable.
The classic layering system is base layer (long underwear) plus mid layer (fleece or puffy) plus shell (waterproof or windproof outer jacket and pants). Each layer has a job: the base manages moisture, the mid layer provides insulation, and the shell blocks wind and precipitation. For more on building a layering system, see our guide to cold-weather layering.
Price Tiers: What to Expect at Each Level
Under $25 covers budget fleece-lined synthetics like PISIQI, WEERTI, HEROBIKER, and the 32 Degrees legging. These are great for everyday wear, moderate cold, and shoppers who want multiple pairs. The trade-off is odor retention and shorter lifespan.
The $25-$75 range covers mid-tier options like the SIMIYA 2-pack and entry-level merino. You get better fabric quality, more thoughtful construction, and access to merino benefits without the premium price tag.
Over $75 covers premium merino sets like the Merino.tech full set and DANISH ENDURANCE. These are built for serious cold-weather use, multi-day trips, and shoppers who want the odor resistance and temperature regulation only merino can deliver.
How to Care for Your Long Underwear
Proper care extends the life of any base layer, but especially merino. Machine wash cold on a gentle cycle, use a mild detergent, and avoid fabric softener, which coats the fibers and reduces moisture-wicking ability. For merino, hand washing is even better if you have the time.
Skip the dryer for merino. Lay flat to dry to prevent stretching and shrinkage. Synthetic thermals can usually handle low tumble dry, but air drying extends their lifespan as well.
Wash less often than you think. Merino can go 3-5 wears between washes thanks to natural odor resistance. Synthetic thermals benefit from airing out between wears rather than going straight into the laundry. For more on extending the life of your gear, see our guide to garment care.
Store long underwear folded, not hung. Hanging stretches out the waistband over time, especially in merino knits. A dedicated drawer shelf or small bin keeps pairs organized and ready to grab on cold mornings.
For more tips on building a long-lasting cold weather wardrobe, see our complete guide to layering for winter.
Activity-Specific Recommendations
For skiing and snowboarding, go with midweight merino like the Merino.tech 250 set, or a synthetic fleece like SIMIYA if you run cold. Both work well under ski bibs and provide the warmth-to-breathability ratio you need on the mountain.
For winter hiking and backpacking, merino is the clear winner because you can wear it multiple days without washing. The DANISH ENDURANCE or Merino.tech sets are both excellent for multi-day trips.
For everyday wear and commuting, lightweight synthetic like the 32 Degrees legging or the PISIQI set is ideal. They fit invisibly under regular clothes and provide noticeable warmth without bulk.
For lounging and pajamas, the HEROBIKER set or WEERTI set are the softest options. Both feel cozy enough to wear all day at home without needing to change.
Frequently Asked Questions
What is the difference between thermals and long underwear?
Should thermals be tight or loose?
What are women’s long underwear called?
Can I wear long underwear for multiple days during a trip?
What is the best long underwear for skiing and snowboarding?
Should I wear underwear under long underwear?
Final Verdict: Which Long Underwear Should You Buy?
After 12 weeks of testing across skiing, hiking, lounging, and everyday wear, the PISIQI Thermal Underwear Set earns our top spot as the best long underwear for women overall. It combines softness, four-way stretch, dependable warmth, and a low price in a way that none of the other seven pairs matched. For shoppers who want one set that handles everything, this is the one.
If you are shopping on a tight budget, the HEROBIKER set delivers surprising softness at a low price. For all-day warmth, the WEERTI fleece set is the plushest option. For merino benefits without the premium price, the Merino.tech 165 shirt or 250 set are the smartest picks. For extreme cold, the SIMIYA 2-pack is the warmest synthetic in the test. For active winter use, the DANISH ENDURANCE merino set is breathable and sustainable. And for invisible everyday layering under regular clothes, the 32 Degrees ultra-light legging is in a class by itself.
Whichever pair you choose from this list of the best long underwear for women, you will be warm, comfortable, and ready for whatever winter throws at you. Stay warm out there.