Making the Best Fitting Socks

Three people in darn tough socks with different heights but the same performance fit

If our socks aren’t the most comfortable, durable, best fitting socks you’ve ever owned, you can return them for another pair.

We hear the most questions and feedback from you about the last piece of that promise – fit. The topic always comes up – it’s constantly on our minds, so we put pen to paper to share what we’ve learned about how socks should fit and why.

What Is Fit?

Comments you might hear in a shoe store…

  • “It’s too loose.”
  • “I can’t even get my heel in.”
  • “They fit, but they’re pinching my toes.”
  • “I’m normally an eight, but can you grab the next size up for these?”

A couple takeaways. First, shoes aren’t one size fits all – neither are socks. If you’ve been buying them that way, chances are your feet would benefit from a change.

Second, fit has layers of meaning. Especially when it comes to clothing and what works on your body. Even when clothing does fit, there’s a sliding scale of how it fits – terms like relaxed, standard, and fitted. Think Crocs® vs. running sneakers.

Defining fit for socks comes down to answering two questions:

  1. Does the sock go on your foot (and lower leg in tall sock styles) and sit as intended?
  2. How closely does the sock hug your skin?

Our size chart can help you answer the first question. Generally, your shoe size is a solid indicator of your sock size, and we’ve got some tips you can use to confirm that further down. These are especially useful if you’re on the line between sizes.

Which brings us to question two: How closely does the sock hug your skin? On your foot, are they loose fitting socks or tight, fitted socks? Then ask, is that how they are designed to fit? If it’s a Darn Tough sock, each sock is designed with what’s called a performance fit.

What Is Performance Fit?

Nordic skier pulling on nordic socks, with a performance fit designed for nordic boots

A performance fit is a next-to-skin fit that closely hugs the foot, flexing and moving with your foot to create one system.

The first time you pulled on a pair of our socks, this probably surprised you, especially if your previous experience was with a six pack of tube socks. Putting our socks on takes effort – in Over-the-Calf styles, akin to pulling on stockings. Compared to cotton tube socks, our socks feel tight.

Compared to, because a performance fit sock that’s the right size for you will not be a tight fit; it won’t squeeze your skin uncomfortably. Instead, it’s a close fit, staying right up against your skin. That’s a fine line, and your first time putting on a pair of performance fit socks, it’s easy to think, “they’re too tight.”

Give it a few hours. Chances are, you’ve forgotten the socks are on. If you haven’t (or if you’d like to double check anyway), we’ve got an easy assessment near the end of this article.

Why (Performance) Fit Matters

You want socks that fit. No explanation needed there. But if you’re being active (running, hiking, skiing, or walking around town) you don’t want a loose fit or even standard fit – you want a performance fit. Here’s why:

Performance fit socks stay in place, greatly reducing bunching, slipping, and sliding issues common in too-loose socks. Even after hours, days, and weeks of wear, our socks keep their shape. They won’t start sagging five days into your thru-hike.


Foot wearing ill-fitting sock vs foot wearing Darn Tough sock with performance fit

Since our socks sit close to skin and move with it (not against it), performance fit also helps reduce friction, which helps to prevent blisters. Reducing friction also cuts back on wear and tear, meaning your socks last longer. That close fit also helps alleviate foot fatigue – especially when you layer in arch support (we do).

Add it all up, and a performance fit sock is a more comfortable sock for high performance activities where support and stability are vital to keeping you at the top of your game. The socks do their job better and help your feet do their job better – overall, it culminates in a better fitting sock.

But we’ve found (and we suspect you will, too), that even when you’re not breaking a sweat, performance fit is still the best fit. No slipping, bunching, or blisters is vital for a marathoner, but it’s a better on-foot experience for everyone, in any activity.

That’s why we knit our socks with performance fit. We’ve tested it, asked professionals to do the same, and we stand behind it. That said, if you want a loose-fitting sock for lazy days (we get it) or for replacing your slippers, go ahead and size up.

How to Make the Best Fitting Socks

We didn’t get performance fit right on our first sock. We believe we have yet to produce our best sock, and part of that is knowing our performance fit can and will be updated and improved again and again.

Runner seated on tailgate wearing darn tough socks with performance fit, like a second skin

But we’ve learned a lot over the years, and you’ve affirmed what we’ve felt on our own feet – once you understand performance fit and why you want it, these socks fit really well. And that fit holds up, longer than might seem possible. It’s not magic, but we’d suggest that there’s an art to it.

Elastic Materials

To flex and move with your foot like a second skin, the sock needs to be able to stretch. To maintain a close fit and proper shape, the sock also needs to be able to rebound back to its unstretched shape. Stretch and rebound. Flex and relax.

The right materials and the right combination of those materials gives our socks this resilience. Merino Wool is a naturally resilient material, able to stretch then rebound a large amount without damage (more on this in our analysis of sock comfort).

We compliment Merino’s natural elasticity with Lycra Spandex elastic. How much elastic and where we put it varies based on the activity category the sock is designed for – because a runner’s sock needs stretch differently than a telephone lineman’s does.

End-Use Design & Features

We knit all our socks with a specific end-use in mind because the way you’ll move your foot and the shoes you’re wearing change what top performance looks like for a sock.

What this could look like:

  • True Seamless™ Toes for a sock that’s truly seamless and an undetectable feel.
  • Ribbed cuffs in our hiking socks that layer Merino over elastic for a sure fit that won’t slide down.
  • Additional elastic around the middle of the sock where it sits on your arch, like a friendly hug that provides arch support and keeps the sock firmly in place at even your top pace.
  • Extended cushion in the toe box of our Steely work socks, for a better, more comfortable fit in the box of safety-toe footwear.
  • Flex windows in specific hike, run, and tactical styles to prevent fabric bunching and keep things smooth.

Not an exhaustive list, but hopefully it conveys the point: we put a lot of thought into making every sock seamlessly fit onto your foot and into your footwear. Like a second skin, remember?

Mountain biker pulling on mountain bike shoes over close-fitting darn tough socks

High-Density Knit

If you have the time and patience to count, you’ll find about 1,441 stitches in a square inch of our socks. That’s what we mean by high-density knit – not that the sock is somehow bulky, but that the stitches are many and tightly packed.

Maybe you’ve heard us mention high-density knit before, as it relates to what makes our socks so durable. But it’s also true that many tiny stitches can conform to your foot and imitate your skin better than fewer large stitches can. More stitches = closer to skin fit.

Proper Washing & Drying

If you took a sock straight off one of our knitting machines, how it fits might not match the size stitched into the cuff. We wash, dry, and board every sock as part of our sock-making process. Not only does this mean you don’t have to worry about your socks shrinking (they’ve already been washed once), but it also is part of how we refine fit.

Darn Tough employee pulling socks out of our washers and dryers

We use different wash and dry settings on different socks based on their materials and stitch styles. Fine tuning these settings let us fine tune the final fit of the sock, a fit that’s checked when the sock is placed on the correctly sized form and boarded, a form of steam drying that helps set the final shape and size.

Every step of the sock-making process determines how our socks fit.

Standards, Checks, & Testing

Darn Tough employees drawing on a sock with a marker during a fit session

When a sock’s knitting journey has been completed, we check our work. To ensure the socks shipping out of our Mill in Vermont are the best fitting socks, we set standards and check socks against them.

Our quality team is passionate and thorough. Every sock size has unique specifications which they check each sock against, testing the measurements, stretch, and rebound.

For new socks, we conduct rigorous on-foot testing. We’re wearing them 30 days, no washing, to make sure that fit holds up day after day. We’re also wearing them, washing (and drying) them, then re-wearing them, checking that fit is continuous wash after wash.

View from above as the Product team does an on-foot fit check session

Your Feedback

We are the Mill. You send us your feedback, and that results in real changes, because we own the process. If a sock isn’t fitting how it should, we take that feedback, seek out the problem, and fix it, all under our roof.

Your feedback has made and continues to make our fit better. Thank you.

Darn Tough socks being placed on correctly-sized forms to check the size and set it

Finding the Right Sock Fit for You

Few feelings are better at the end of the day than happy feet. Proper fitting socks play a huge role in achieving that feeling. We know that feeling, we love it, and we want you to have it.

How Do I Tell If I Purchased the Right Sock Size?

First, check our Size Chart. Then, these basic checks can confirm your sock is the right size:


Your heel should sit squarely in the heel bed. This is easiest to check on our socks that have a contrasting heel color, but you can confirm this on any sock by looking closely at the heel area.

On either side, you’ll see a diagonal line where the stitches coming down from the cuff meet with the stitches running along the bottom of your foot. When your foot is placed flat on the floor, the end of this line should point back to the end of your foot, like it’s running off your heel. The line should roughly cut your heel in half diagonally.

If your sock is too big, the heel area will ride up your Achilles. Too small, the heel bed won’t be centered on your heel.


We join our toes with loops for a seamless fit, and you can use those loops as another fit check. Look for them above the “Darn Tough” name stitched into your socks.

The loops should be sitting on top of your toes, lying flat. If excess fabric is bunching, the sock’s likely too big. Flex your toes – if the sock moves with them, all set. If the resistance from the sock is so strong you can’t flex your toes, the sock is too small.

How Do I Tell If My Socks Are Too Tight?

The best test is to wear them for a full day. If you’ve forgotten they’re on by the end of the day, chances are they’re not too tight – they’re snug, and that snug, close fit is good. If you’re still unsure, ask yourself these three questions:

  1. Are your feet uncomfortable?
  2. Are you experiencing any pain, tingling, or loss of sensation?
  3. When you flex your toes, does the sock stretch to make room, then rebound back when you unflex?

If you answered no to the first two questions and yes to the last, chances are you have the right size sock.

Notice we didn’t mention discoloration or dents in your skin. Performance fit socks are a close fit – and if you’re dehydrated, a close fit can cause slight skin discoloration or denting. It’s normal and typically not a sign of too tight socks. If, however, the discoloration is severe or the dents are deep, you may need a larger size.

Pro Sizing Tips

Our size chart is a good guide, but it’s not perfect. Here’s a couple tips if you’re not sure which size to buy, or the one you bought isn’t working out:

  • Between sizes? Size up. If you’re right on the line between two sizes, that performance fit means you can size up without fear of your foot swimming around.
  • On the top end of the size range? Maybe you’re in the size range, but near the top end. A couple things to consider. If you’re purchasing a sock with cushion, especially full cushion, those terry loops are added to the inside of the sock. You may want to size up. If you wear a wide shoe, again, you may want to size up for some additional stretch.
  • How tall is the sock? If you have wide calves, you may find you wear one size in our shorter socks but want to size up in our taller socks, especially Over-the-Calf.
  • We size our socks based off Men’s and Women’s shoe sizes… but we wear both regardless. Just know Men’s styles tend to rise a tad higher on the leg.
  • Got tiny feet? Try our Kids’ styles.
  • Got large feet? We knit XXL for you.

Don’t Take Our Word for It

Once you get used to it, performance fit makes for the best fitting socks. At least, that’s what you tell us.

"When I put on the socks, they are a little snug and go on like stockings, but they loosen up in 30 minutes to an hour to an absolutely perfect fit to the point that I have to think about whether or not I'm wearing the socks. I love them." — Jennifer L.
"Best form-fitting (comfortable) socks I've ever worn. When I first started pulling on these socks, I thought, "Oh, no, I'm not going to be able to get these on!" But they went on my foot and all the way up my calf with little effort, and fit like a second skin all day. That night, when I took the socks off, there were no lines or puffiness anywhere. I'm impressed." — Jane C.
"Finally! First socks that fit perfectly and stay above my boot line all day long! Thank you!" — Davin N.
"Once I discovered Darn Tough socks every other brand was of inferior quality. These socks fit like a dream and are very comfortable - without toe seams to chafe and cause blisters. After washing they look like new. They just seem to last for years! I love these socks! — Christine L.
"I have worn only darn tough socks for around 6 months and I won't wear anything else from now on. They are by far the best made and comfortable socks I have ever tried. You cannot feel any seams whatsoever and they FIT RIGHT, I wear a size 9 and the mediums are just right." — Joe C.
"Love the XXL socks! At last, socks for large feet! What a difference to actually have socks that fit, and these are so comfortable. Perfect for my daily walks." — Al V.

Socks That Fit: Our Promise

Piles of the best fitting socks, made by Darn Tough, ready to be packaged and shipped

We’re committed to making the best fitting socks, and your feedback makes us better. If you purchased the wrong size, we offer free shipping on all our returns and exchanges. Our Customer Service team is also ready and eager to help you find a sock that fits you perfectly.

Fit should last a lifetime. If our socks lose their fit, you can return them at any time for a new pair, whether that’s five years from now, 15, or 50. That’s our Unconditional Lifetime Guarantee – and we stand behind it.