6 Best Long Johns For Backpacking Trips That Won’t Chafe or Overheat

You’re three hours into a cold, misty climb, and the sweat from your uphill push is starting to feel clammy and cold. Worse, a nagging seam on your long johns is rubbing your hip raw under your pack’s waist belt. The right base layer could have prevented this, turning a miserable slog into a comfortable, focused hike.

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Why Your Base Layer Choice Matters on the Trail

Think of your long johns—your base layer bottom—as your second skin. Their primary job is moisture management, pulling sweat away from your body to keep you dry. When you stop moving on a cold day, that moisture can chill you to the bone, fast.

A good base layer also provides insulation without causing you to overheat the moment the trail turns uphill. The goal is a steady, comfortable microclimate, not a swampy sauna followed by a flash freeze. Chafing is the other enemy here. Poorly placed seams, baggy fits, or rough fabrics can create hotspots that turn into painful raw patches under the constant friction of a pack and movement. This isn’t just about comfort; it’s about preventing misery that can cut a trip short.

Smartwool Intraknit Merino for a Chafe-Free Fit

Imagine climbing a steep, rocky pass where you need total freedom of movement. That’s where the seamless construction of Smartwool’s Intraknit line really shines. By using a 3D knitting process, they eliminate most traditional seams, which are the number one cause of chafing under a hip belt or harness.

These bottoms also feature body-mapped ventilation, with more breathable panels in high-heat zones like the groin and behind the knees, and more insulation over the quads. This targeted approach means less overheating on the ascent and more warmth when you stop for a break. They are an investment, but for long-distance hikers or anyone sensitive to friction, the engineered fit is a game-changer.

Patagonia Capilene Midweight‘s Versatility

You’re on a multi-day trip in the Pacific Northwest, where you’re guaranteed a mix of drizzle, sweat, and chilly nights. Patagonia’s Capilene Midweight is the workhorse you want for these conditions. Made from 100% recycled polyester, this synthetic fabric is a master of wicking moisture and drying incredibly fast.

Unlike merino wool, it won’t hold onto moisture for long, making it a great choice for damp climates or trips where you might need to wash and dry your layers on the go. The smooth face fabric layers easily under hiking pants or rain pants without bunching up. While synthetics can get smelly faster than wool, the HeiQ Pure odor control does a respectable job, and its durability is a major plus for those who are tough on their gear.

Icebreaker 200 Oasis for Classic Merino Comfort

For that classic, next-to-skin softness and incredible temperature regulation, it’s hard to beat pure merino wool. The Icebreaker 200 Oasis is the standard-bearer for a reason. It’s the perfect companion for a fall backpacking trip in the Rockies, where mornings are frosty but afternoons can be surprisingly warm.

The 200-weight merino fabric hits the sweet spot for three-season use, providing solid warmth without feeling bulky. Its greatest superpower is its natural odor resistance; you can wear these for days on end without offending your tent mates. The flatlock seams and gusseted crotch help with mobility and chafe-prevention, making this a reliable, comfortable choice for almost any adventure.

Arc’teryx Rho LT for High-Output Activities

Picture yourself skinning up a mountain for a backcountry ski descent or fastpacking along a ridgeline in biting wind. You’re working hard and generating a massive amount of heat and sweat. The Arc’teryx Rho LT (Lightweight) is built for exactly this scenario.

Its Torrent™ fleece-backed fabric is exceptionally good at pulling moisture off your skin while providing a surprising amount of warmth for its weight. The real magic is its stretch and articulation, which move with you like they’re not even there. This is a technical piece for high-output pursuits where moisture management and freedom of movement are the absolute top priorities.

REI Co-op Merino 185: An Excellent Value Pick

You don’t need to spend a fortune to get the benefits of merino wool. The REI Co-op Merino 185 line is proof of that. This is the perfect first pair of merino long johns for someone building their gear closet or the budget-conscious backpacker heading out for a weekend trip.

At a 185 g/m² weight, it’s technically a lightweight layer, making it incredibly versatile for everything from cool summer nights to a base for winter layering. It delivers on merino’s core promises: solid warmth, next-to-skin comfort, and good odor control. While it may lack the fancy 3D-mapping or specialized fabrics of premium options, it provides 90% of the performance for a fraction of the cost.

Outdoor Research Echo for Warm Weather Hiking

Long johns in the heat? Absolutely. When you’re hiking through overgrown trails in buggy territory or exposed to relentless sun above the treeline, a full-length, ultralight layer is your best defense. The Outdoor Research Echo bottoms are designed for this specific purpose.

Made from an incredibly light, breathable, and fast-drying polyester, they feel cooler than wearing nothing at all. They offer UPF sun protection and a physical barrier against mosquitoes and ticks without causing you to overheat. Think of them less as insulation and more as active protection for warm, exposed, or buggy environments.

Fabric & Weight: How to Choose Your Ideal Pair

Choosing the right pair comes down to two key factors: the material and its weight. There’s no single "best" option, only what’s best for your trip. Don’t get bogged down in analysis; just match the gear to the conditions you expect.

First, consider the fabric. This is a fundamental choice between natural and synthetic fibers.

• Merino Wool: Breathes well, provides warmth even when damp, and is impressively odor-resistant. It can be less durable and slower to dry than synthetics.
• Synthetics (Polyester/Nylon): Excel at wicking sweat and dry extremely quickly. They are typically more durable and affordable but can start to smell after a day of hard use.

Next, look at the fabric weight, usually measured in grams per square meter (g/m²). This tells you how warm it will be.

• Lightweight (under 185 g/m²): Best for high-output activities or three-season use. Excellent for managing sweat and taking the edge off a cool breeze without causing overheating. The OR Echo is an extreme example of this.
• Midweight (200-260 g/m²): The all-around sweet spot for most cold-weather backpacking. Provides significant warmth for chilly nights and cold days but still breathes well enough for active use. Most of the options on this list fall here.
• Heavyweight (260+ g/m²): This is specialized gear for deep winter, mountaineering, or very cold, low-activity situations. For most backpacking, it’s overkill and will lead to overheating.

Ultimately, your choice depends on the expected conditions and your personal metabolism. If you run hot or hike in damp places, lean towards a lighter weight or a synthetic. If you prioritize odor control and comfort for a multi-day trip in dry, cold weather, a midweight merino is a fantastic choice.

The perfect pair of long johns won’t make the mountain smaller or the rain stop, but they will make you more comfortable while you’re out there. Don’t let the pursuit of perfect gear stop you from getting on the trail. Pick a pair that makes sense for your next trip, pack your bag, and go have an adventure.