Best Long Johns for Men and Women in 2026

The best long johns for most people are the Smartwool Classic Thermal Merino Base Layer Bottom. They stay warm without feeling bulky, breathe well across a wide temperature range, and outlast cheap thermal underwear in both comfort and odor control. For this guide, I focused on long johns that hold up in real life — under jeans on a cold commute, under ski pants on a weekend trip, in a drafty house, or during winter workouts.

If you want one short answer, merino wool long johns are still the safest premium buy in 2026. But not everyone needs merino. Some people need a budget thermal base layer, a tougher workwear option, or soft thermal underwear for sleep. The picks below are organized by use case so you can buy the right pair of long johns the first time.

Our Top Picks

Smartwool Classic Thermal Merino Base Layer Bottom — Best Overall Long Johns

$95–$120 — check price on Amazon

Downsides: They cost significantly more than synthetic long johns, and merino wool requires gentler washing than a toss-it-in-anything gym layer.

If you only buy one pair of long johns this season, start here. Smartwool gets the balance right: enough warmth for real winter weather, enough breathability for all-day wear, and far better odor resistance than most polyester thermal underwear. The merino fabric feels soft against skin and layers cleanly under jeans, snow pants, and relaxed work trousers.

There is a reason merino base layers keep showing up in recommendations from gear-focused outlets like Wirecutter. For a clear primer on how base layers work and when to choose wool vs synthetic, see REI's base-layer guide. They work across more situations than most fabrics. This Smartwool pair is especially easy to live with — the fit is close without feeling restrictive, and the seams and waistband are far less irritating than what you get from bargain thermals.

• Why I like it: Strong warmth-to-weight ratio, natural odor resistance, soft hand-feel, and clean layering for casual or active use.
• Who should skip it: Anyone who wants the lowest price or is rough on delicate wool garments.

32 Degrees Heat Performance Baselayer Legging — Best Budget Long Johns

$15–$25 — check price on Amazon

Downsides: Less warm, less odor-resistant, and typically shorter-lived than a quality merino base layer.

Cheap long johns often miss on fit, fabric feel, or both. This pair beats most low-cost options because it stays light, stretchy, and easy to wear under normal clothes. If your goal is simple winter layering — not backcountry performance — that matters more than premium fabric bragging rights.

The synthetic fabric dries quickly and adds minimal bulk, so these thermal leggings work well for office wear, weekend use, or packing as a backup base layer (pair with compact packing cubes for tidy travel). They also let you test whether long johns are something you will wear regularly before committing to a pricier pair.

• Why I like it: Low price, smooth layering under clothes, quick dry time, and enough stretch for everyday comfort.
• Who should skip it: Anyone who needs serious insulation for long stretches below freezing.

Icebreaker 200 Oasis Leggings — Best Merino Upgrade

$100–$130 — check price on Amazon

Downsides: The athletic fit can feel too trim for lounging, and the price sits firmly in premium territory.

Icebreaker's 200 Oasis leggings are the long johns to buy if you want merino but prefer something more technical and body-mapped than the Smartwool pick. The midweight merino wool fabric regulates temperature well, and the trimmer cut works nicely under shell pants or tapered everyday trousers.

These thermal base layers also pack well for trips and feel less swampy during stop-and-go movement than many heavier long johns. The gusseted construction improves mobility, and the overall design suits people who run warm but still need a real cold-weather base layer.

• Why I like it: Excellent temperature regulation, athletic fit, quality merino wool, and strong performance for travel or active use.
• Who should skip it: Anyone who prefers a roomier, lounge-first fit.

Thermajohn Ultra Soft Thermal Underwear Pants — Best Long Johns for Lounging and Sleep

$20–$30 — check price on Amazon

Downsides: The plush fabric is bulkier than performance long johns and can feel too warm indoors for some people.

Some long johns are built for miles on a trail. These are built for comfort on cold nights and slow mornings. The brushed interior works well for sleep (pair with a blackout sleep mask), home office wear, and lounging in a chilly house. If that is your use case, there is no reason to overbuy a technical merino pair.

They are also forgiving in fit and easy on the budget. You give up sleekness under slim pants, but that is the tradeoff. If your priorities are softness, warmth, and comfort at home, these thermal underwear pants are more satisfying than a tighter athletic base layer.

• Why I like it: Cozy brushed interior, good value, comfortable stretch, and strong sleepwear appeal.
• Who should skip it: Anyone who wants low-bulk long johns for fitted pants or hard training.

Under Armour Base 3.0 Leggings — Best Long Johns for Cold-Weather Workouts

$50–$70 — check price on Amazon

Downsides: The synthetic feel is less cozy than merino wool, and odor can build faster with repeated sweaty use.

For winter workouts, the best long johns are not always the warmest. They need to hold heat while still moving moisture away from skin. This Under Armour pair is built for motion — snug fit, brushed interior, and far less clammy than most cheap synthetic thermals.

If you run, hike, shovel snow, or walk long distances in the cold, these thermal leggings are easier to wear than thicker casual long johns. They dry fast, bunch less under outerwear, and stay stable as your body temperature shifts — exactly what you need during active winter use.

• Why I like it: Good moisture management, athletic cut, useful warmth, and minimal bulk under outerwear.
• Who should skip it: People who want natural fibers or soft sleepwear comfort.

Carhartt Force Midweight Classic Thermal Base Layer Pant — Best Long Johns for Workwear

$35–$50 — check price on Amazon

Downsides: They feel more rugged than refined, and they are not the sleekest option under slim everyday clothes.

This Carhartt pair is less about luxury and more about practical winter performance. The fabric has enough heft for outdoor chores, job sites, and long hours in cold conditions, while the moisture-wicking construction is a clear upgrade over old-school cotton waffle knit thermals.

If your long johns live under canvas work pants, insulated overalls, or rougher outerwear, durability matters as much as softness. That is where this thermal base layer stands out. It is not elegant, but it is the smart pick for buyers who need tough, dependable thermal underwear.

• Why I like it: Rugged construction, dependable midweight warmth, solid moisture management, and work-ready durability.
• Who should skip it: Anyone who wants thin, nearly invisible thermal underwear for office outfits.

Buying Guide: How to Pick the Best Long Johns

Where will you actually wear your long johns?

The best long johns for skiing are not the best pair for sitting at a desk or sleeping in a cold bedroom. For daily wear under jeans or chinos, look for a trim fit, soft fabric, and low-bulk seams that do not show through pants.

For lounging or sleep, comfort matters more than technical performance. For hiking, running, or snow sports, breathability and moisture management take priority over raw warmth.

Merino wool or synthetic long johns — which is right for you?

Merino wool long johns cost more, but they regulate temperature well and resist odor naturally. They are the stronger choice for travel, repeated wear, and buyers who dislike the slick feel of polyester thermal underwear.

Synthetic long johns are cheaper, faster drying, and easier to maintain. They make more sense for workouts, tighter budgets, or rougher use where you need a base layer you can wash without thinking twice.

How warm should thermal underwear actually be?

Do not default to the heaviest pair. Long johns that are too warm will cause overheating indoors, sweating during movement, and eventually you stop wearing them. For most people, lightweight to midweight thermal underwear is the sweet spot.

Heavyweight long johns work better for very cold climates, long periods of standing still outside, or sleeping in an unheated room. Match the weight to your actual conditions, not your worst-case scenario.

What fit works best under regular clothes?

Good long johns should sit close to the body without pinching or twisting. A sloppy fit bunches at the knees and feels annoying fast. Flat seams, gusseted construction, and a waistband that stays put are worth paying for.

If you wear slim pants, avoid plush interiors and bulky cuffs. If the pair is mainly for home use, a slightly more relaxed fit can feel better for all-day comfort.

How much should you care about washing and durability?

More than most product pages suggest. Some merino long johns need gentler washing and careful drying to avoid shrinkage. Synthetic thermal underwear is usually simpler if you want a low-maintenance base layer you can machine wash freely.

The best long johns are the pair you will actually wash and wear consistently. A slightly less premium fabric can be the smarter buy if it fits your laundry habits and gets used every week.

How many pairs of long johns do you need?

For occasional winter use, one solid pair is enough. If you wear long johns for commuting, outdoor work, or exercise several times a week, two or three pairs make life easier and extend the life of each pair.

A practical setup: one premium merino pair for all-day comfort, one cheaper synthetic pair for harder use or workouts, and one soft pair for sleep if you tend to run cold at night.

If you want the safest pick, buy the Smartwool pair. If you want solid value, start with 32 Degrees. If your priority is staying warm at home or during sleep, go with the Thermajohn. And if you are building a full winter layering system, explore related cold-weather gear to complete your setup.