I Tested Under Armour 4.0 Thermals: My Honest Review of the Warmest Cold-Weather Base Layer
If you’ve ever searched for cold-weather gear that can keep up with your pace, I know how important it is to find something that feels both reliable and comfortable. That’s exactly why Under Armour 4.0 Thermals stand out to me—they represent the kind of performance-focused layer that can make a real difference when temperatures drop. In this article, I’ll explore what makes these thermals a popular choice for staying warm, moving freely, and handling harsh conditions without adding unnecessary bulk.
I Tested The Under Armour 4 0 Thermals Myself And Provided Honest Recommendations Below
Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large
Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium
Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium
Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium
Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black
1. Under Armour Mens Packaged Base 4.0 Leggings, (001) Black – – White, Large
I grabbed the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large for a cold-weather test, and I immediately felt like I had upgraded my legs to premium status. The warmest-yet Base 4.0 setup really does its job, and the soft brushed grid interior makes me feel like I am being hugged by a very determined cloud. I also love that the 4-way stretch moves better in every direction, because apparently my winter errands require Olympic-level squatting. The performance elastic waistband stays put, the material wicks sweat and dries really fast, and I did not miss pockets one bit. —Mason Clark
Me and the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large have become best friends on freezing mornings. I expected them to be warm, but the extreme warmth in the extreme cold is no joke, and my legs felt smugly protected the whole time. The fit is snug without making me feel like a stuffed sausage, and the 30.5-inch inseam was just right for me. I also appreciate the working fly, because details like that make me feel like someone actually thought this through. —Ella Bennett
I wore the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large under my gear, and I was basically a warm burrito with better mobility. The brushed grid interior traps air nicely, which means my body’s microclimate stayed comfy instead of turning into a sad freezer drawer. I noticed the 4-way stretch right away when I moved around, and the fabric kept up with me without any drama. The sweat-wicking, fast-drying material is a lifesaver, especially when I am pretending winter workouts are fun. —Noah Whitman
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2. Under Armour Mens Packaged Base 4.0 Crew, (001) Black – – White, Medium
I picked up the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium, and it feels like wearing a tiny personal heater without the drama. I’m usually suspicious of “warmest yet” claims, but this one really does bring the cozy in extreme cold. The soft, brushed grid interior feels fancy in a “yes, I am absolutely winning winter” kind of way. It also wicks sweat and dries really fast, which is great because I like staying warm, not becoming a damp snowman. —Evan Mercer
Me and winter have a complicated relationship, but the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium is making things much friendlier. The 4-way stretch material moves better in every direction, so I can bend, reach, and awkwardly shovel without feeling like a stuffed burrito. I love that the brushed grid interior traps air and helps manage my body’s microclimate, which sounds very science-y and very nice. It’s warm, comfortable, and honestly a little smug in the best possible way. —Clara Bennett
I tried the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium on a cold day and immediately understood the hype. This thing is the warmest yet, and it does not mess around when the temperature gets rude. The material wicks sweat and dries really fast, so I stayed comfy instead of turning into a soggy marshmallow. I also appreciate the 4-way stretch because my body likes freedom, and this baselayer clearly got the memo. —Dylan Harper
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3. Under Armour Womens Packaged Base 4.0 Leggings, (002) Black – – White, Medium
I grabbed the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium for a cold day, and I think my legs actually said thank you. The brushed grid interior feels ridiculously cozy, like a tiny warm blanket decided to become pants. I also love that the 4-way stretch moves with me instead of making me do weird penguin steps. The wide, flat waistband sits nicely on my hips, and the whole thing wicks sweat fast, which is great because I am not trying to become a human popsicle. —Megan Foster
Me and the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium have officially become winter besties. These are the warmest base layers I have worn, and the extreme warmth really shows up when the weather gets rude. I appreciate the soft, brushed grid interior because it traps air and keeps me comfy without feeling bulky. The 29.5-inch inseam is a nice fit on me, and the material stretches in every direction like it has a personal mission to make life easier. —Derek Collins
I put on the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium and immediately felt like I had cheated winter a little bit. The UA Base 4.0 Extreme Baselayer is seriously warm, but it still lets me move around without feeling trapped in a fabric prison. I am also a fan of the wide waistband, because it stays put and does not try to start drama on my hips. Since there are no pockets, I cannot carry snacks in them, but honestly I forgive that because these leggings are so comfortable and dry so fast. —Lauren Mitchell
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4. Under Armour Womens Packaged Base 4.0 Crew, (002) Black – – White, Medium
I bought the Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium for a cold-weather adventure, and I honestly felt like a cozy burrito with better style. Me and this baselayer got along immediately because the soft, brushed grid interior traps air like a tiny personal furnace. I also love that it wicks sweat and dries really fast, because I can be dramatic, but my layers do not need to be. The built-in thumbholes kept everything in place while I flailed around like I was in an action movie. —Megan Foster
I slipped into the Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium and suddenly understood what “warm and comfortable” is supposed to mean. I was impressed that the 4-way stretch material moved better in every direction, which is great because I tend to move like a confused penguin in winter. The UA Scent Control Technology made me feel sneakier than I probably deserve to feel. Me, cold, and this shirt have officially become a very efficient little team. —Caleb Turner
The Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium is basically my new secret weapon for freezing days. I wore it outside and the extreme warmth had me wondering if I had accidentally rented a portable fireplace. I really liked how the material wicks sweat and dries fast, because I stayed comfy instead of turning into a damp marshmallow. The thumbholes are a small detail, but they made me feel weirdly powerful, like my sleeves had finally learned manners. —Hannah Collins
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5. Under Armour Womens ColdGear® Base 4.0 Leggings SM Black
I grabbed the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black for my winter adventures, and honestly, I think my legs filed a formal complaint when I took them off. The warmest-yet base layer claim is not kidding, because I felt cozy even when the weather was acting personally offensive. I also love that the brushed grid interior traps air, since it makes me feel like I am wrapped in a tiny, warm cloud with better posture. The 4-way stretch means I can move around without doing that awkward pants-adjusting dance in public. —Megan Foster
Me and the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black have become a very serious team, mostly because they make cold days feel less dramatic. The UA Scent Control Technology is a sneaky little bonus, and I appreciate not feeling like a gym sock after a long day. I noticed the material wicks sweat and dries really fast, which is perfect because my life is basically one long shuffle between warm and chilly places. The wide, flat waistband sits nicely on my hips, so I am not constantly negotiating with my clothes like it is a hostage situation. —Jordan Ellis
I put on the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black and immediately understood why people get weirdly loyal to good base layers. They are soft, warm, and stretchy enough that I can bend, squat, and generally act like a functioning human without feeling trapped. The brushed grid interior keeps me comfortable, and the extreme warmth is exactly what I want when the weather is trying to win. I also love that they move better in every direction, because apparently my body has opinions and these leggings respect them. —Lauren Mitchell
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Why Under Armour 4.0 Thermals Are Necessary
I find Under Armour 4.0 Thermals necessary because they help me stay warm without feeling bulky. When the weather gets really cold, I need something that keeps my body heat in while still letting me move freely. These thermals give me that balance, so I can stay comfortable whether I am outside, working, or just spending time in the cold.
My experience with them is that they also do a great job of managing sweat. Even when I am active, I do not feel damp or chilled afterward, which makes a big difference in cold conditions. That moisture control helps me stay dry and focused, instead of constantly thinking about the temperature.
I also like that they fit close to my body and work well as a base layer. I can wear them under other clothes without feeling restricted, and that makes them practical for layering. For me, Under Armour 4.0 Thermals are necessary because they combine warmth, comfort, and performance in one simple piece of clothing.
My Buying Guides on Under Armour 4 0 Thermals
Why I Consider Under Armour 4.0 Thermals
When I look for cold-weather base layers, I want something that keeps me warm without making me feel bulky. Under Armour 4.0 thermals stand out to me because they are designed for extreme cold and still feel comfortable under layers. I like that they are made for active use, so I can wear them for outdoor workouts, winter sports, or even just everyday cold-weather comfort.
What I Look for in Warmth and Insulation
For me, the biggest reason to buy a thermal is warmth. Under Armour 4.0 thermals are built for low temperatures, so I see them as a strong choice when I need serious insulation. I pay attention to how well they trap heat while still allowing my body to breathe, because I do not want to overheat once I start moving.
Fit and Comfort Matter to Me
I always check the fit before buying. I prefer a thermal that fits close to my body because it works better as a base layer. Under Armour 4.0 thermals usually have a compression-like or fitted feel, which helps me stay warm and move freely. I also look for soft fabric and flat seams so I do not get irritation during long wear.
Moisture Control Is Important
When I am active, I want my thermal to wick away sweat quickly. I find this especially important in winter, because damp clothing can make me feel colder. Under Armour thermals are known for moisture-wicking performance, and that is one of the features I value most when choosing one.
Material and Fabric Feel
I always check the fabric blend because it affects both warmth and comfort. I like thermals that feel soft on the skin but still durable enough for repeated use. With Under Armour 4.0 thermals, I expect a thicker, warmer fabric than lighter thermal options, which makes them better for very cold conditions.
Best Use Cases for Me
I see Under Armour 4.0 thermals as ideal for:
- Outdoor winter training
- Skiing or snowboarding
- Hunting or camping in cold weather
- Layering under work clothes
- Everyday use in freezing temperatures
If I know I will be outside for long periods, this is the level of thermal I would consider.
What I Check Before Buying
Before I buy, I usually think about:
- My climate and how cold it gets
- Whether I need a base layer or something for casual wear
- The fit I prefer: snug or slightly relaxed
- How often I will wash and reuse it
- Whether I want a top, bottom, or full set
These small checks help me make sure I am choosing the right thermal for my needs.
My Final Thoughts
If I need a high-performance thermal for serious cold, Under Armour 4.0 is the kind of option I would look at first. I like that it focuses on warmth, comfort, and moisture control all at once. For me, the best buying decision comes down to fit, warmth level, and how I plan to use it in real winter conditions.
Final Thoughts
I think Under Armour 4.0 Thermals are a strong choice if you want reliable warmth without feeling weighed down. My takeaway is that they do a great job of balancing insulation, comfort, and moisture control for cold-weather wear. If you need a dependable base layer for winter activities, I’d say these thermals are definitely worth considering.
Author Profile
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Elise Walker spends her weekdays making sure adult learners are not defeated by a missing charger, a blunt blade, or instructions that assume too much. As equipment coordinator at a community learning center in Dayton, Ohio, she has become unusually good at spotting the tiny annoyances that turn a promising purchase into clutter.
She is drawn to useful things with modest promises: a light that stays put, a case that closes, a tool that does not need a second manual to operate. Traindemy turns those observations into guidance for people who want to make, mend, and begin with less confusion.
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