8 Best Thermal Underwear of 2026

Thin is the trick here. The waffle knit is the lightest of the sets on this list, and that’s exactly why it works under dress pants and slim jeans, where a beefier thermal shows through at the knee.

It’s cut close through the body and the legs, so it layers without bunching, and the warmth is middling for this group — plenty for a cold commute, a dog walk or a day of errands, not what we reach for to stand around outdoors.

The cuffs are the one detail we’d change if we could. They aren’t especially elastic, so sleeves and ankles creep up over a day of movement; tucking them under a glove cuff or a sock sorts it.

Where the set wins is the price of admission: it’s the cheapest full set here and it doesn’t feel like a compromise under clothes. This is the one we hand someone buying their first base layer, and it’s enough for a city trip. Step up to the Convallaria set when the cold is the point of the trip rather than an inconvenience.

The first thing we noticed was the hand-feel: smooth and soft, closer to a well-worn flannel shirt than to the slick synthetics in this group. That’s why these ended up in the wear-them-around-the-house pile as well as the layering pile.

Midweight is the right label. They’re warm under jeans without a visible bulk line, and the wicking finish keeps them from going clammy when you’re moving — a commute, a walk, an hour with a shovel. Sitting still in real wind is where a heavier bottom earns its money.

The waist sits high, which we liked for keeping the lower back covered under a short jacket, though the rise will feel generous on a short torso. As a bottom you can wear for a whole day without thinking about it, nothing else here comes close.

These cost more than any other bottom in this guide, by a margin you’ll notice at checkout. The fair question is whether the extra buys anything, and the answer is warmth, with a couple of conditions attached.

The waffle knit is denser than the Duofold and the Fruit of the Loom, and it’s the pair we reach for when the day involves standing around in serious cold — a job site, a breakdown, a long wait outdoors — rather than moving through it. That density has a cost: these are warmer than you want at a desk, so they aren’t the pair for an office commute.

For anyone who’s outside in it all day, we think the money is justified, and for everyone else the cheaper bottoms do the job. It’s the clearest case in this group of paying for a specific capability rather than a name on a waistband.

They run large through the hip and the waist sits snug, so if you want them under slim work pants, take the smaller of two sizes. The generous leg length is a bonus over a boot.

Fleece-lined leggings do something long johns can’t: they’re warm next to the skin and still look like something you meant to wear. If you want one layer that handles a winter run, the walk to the trailhead and the errands after, this is the pair.

The lining is thin but genuinely warm, and it doesn’t add a bulk line under jeans, which is the usual failure of fleece leggings. Pockets are the detail we didn’t expect to care about — a phone and a key in the layer you’re already wearing means one less thing in your hands.

The waistband is high and holds you in, which most of us liked and anyone short in the torso will find is a lot of rise. It also stays put better in a snug size than a relaxed one, so resist the urge to go up twice. Cheaper fleece sets exist; the stretch and the pockets are what you’re paying for here.

This is the least expensive full set in the women’s half of this guide, and on warmth it gives away very little to the pair that costs more.

The fleece lining is soft against the skin and thin enough that jeans go over the top without a fight. We wore the set under denim and under snow pants and never felt like the layer was the problem; as pajamas on a cold night it’s better than it needs to be, and it sits under a skirt without a line.

Check the fabric the day it arrives. Some sets come through thinner than the fleece-lined photos suggest, and it’s easier to send them back in October than to discover it in January. Where it is thick, it’s a genuinely warm set for very little money.

Four or five tops in one order changes how you use a base layer. Instead of rationing the one good thermal shirt, you keep one in the truck, one in the gym bag, one in the drawer, and midweek laundry stops being an emergency.

The shirts themselves are thin, close-fitting and warmer than their weight suggests — the fleece inside does the work, and the smooth outside lets a shirt or hoodie slide over the top instead of catching on it.

We think the pack is the right buy for someone who wears a base layer most days: a job, a barn, a winter commute. It’s overkill for a single ski weekend. They’re cut to compress, so order your normal size only if you want it snug.

The legs on these run longer than the price suggests. For anyone who usually finds long johns stopping short of the boot, that extra length is the reason to look here rather than at the pricier waffle knits.

Warmth is decent rather than outstanding: the waffle traps air well under jeans, and the texture is soft enough that we stopped noticing it within a minute of putting it on. It doesn’t chafe, which is more than we can say for some heavier knits.

Sizing runs large and the waist is the loosest part, so order down rather than up. If you’re between sizes, take the smaller one and skip the belt battle.

What this bottom is, then, is the least expensive way to add real warmth under work pants or ski bibs, and the best of the budget bottoms here if length is your problem. For a cold commute under jeans, it’s more than enough.