Order the COOPS letter that matches the US size you wear in sneakers. Each letter covers two US sizes, so a women’s 10 and 10.5 are both an S. If you sit between two letters, or your feet are wide, go one letter up.
Sizing questions come up a lot, and it makes sense. COOPS use letters (5XS to 5XL) instead of the numbers on every other shoe box in your closet, and nobody wants to guess on something they’re going to wear all day. So here is exactly how it works, how to measure if you want to be sure, and what to do if your feet don’t fit neatly into a chart.
Why COOPS use letter sizes
A knit upper stretches. A leather or mesh sneaker mostly doesn’t, which is why those come in half sizes and widths. Because the COOPS upper gives a little in every direction, one letter comfortably covers a full size and the half above it. That’s the whole idea behind the letters: fewer sizes, and much less chance of landing between two of them.
It also means one letter works for women’s and men’s feet. The toggle on the product page only changes which US numbers you’re reading against. The shoe is the same.
The COOPS size chart
| COOPS | Women’s US | Men’s US |
|---|---|---|
| 5XS | 5 to 5.5 | n/a |
| 4XS | 6 to 6.5 | 4.5 to 5 |
| 3XS | 7 to 7.5 | 5.5 to 6 |
| 2XS | 8 to 8.5 | 6.5 to 7 |
| XS | 9 to 9.5 | 7.5 to 8 |
| S | 10 to 10.5 | 8.5 to 9 |
| M | 11 to 11.5 | 9.5 to 10 |
| L | 12 | 10.5 to 11 |
| XL | n/a | 11.5 to 12 |
| 2XL | n/a | 12.5 to 13 |
| 3XL | n/a | 13.5 to 14 |
| 4XL | n/a | 14.5 to 15 |
| 5XL | n/a | 15.5 to 16 |
High Top and Low Top share the same sole and fit, so your letter is the same in both.
How do I measure my feet at home?
If you already know your sneaker size, you can skip this. If you’re not sure, or you’ve been wearing the same size since high school (a lot of us have), it takes two minutes:
- Put a sheet of paper on a hard floor, pushed up against a wall.
- Stand on it with your heel touching the wall, wearing the socks you’d normally wear, or none if you plan to go barefoot.
- Have someone mark the tip of your longest toe. It isn’t always the big toe. Keep the pencil straight up and down.
- Measure from the wall to the mark. Do both feet and use the longer one.
- Match the length to the chart on our size guide.
Do it in the evening if you can. Feet change a little over the day: in one MRI study, foot volume went up over a day of sitting and came back down when people put their feet up.1 A size that fits at 6pm is a size that fits all day.
I’m between two letters. Which one?
Take the larger one. The extra length gives your toes room to spread, and the stretch knit keeps the shoe snug around the rest of your foot, so it won’t feel loose.
What if I have wide feet?
Go one letter up from your usual size. The upper has no stiff panels, so it widens across the ball of the foot, and the extra letter stops the knit from pressing. We wrote a whole post on this: sock shoes for wide feet.
How should COOPS feel when they fit?
Snug like a sock, with room to wiggle your toes. A little tight out of the box is normal, that is the knit doing its job. Give them a few wears and it relaxes slightly and molds to your foot, then it holds. You don’t need to size down to account for that.
If your toes touch the front or the knit presses on the sides after a few days, you’re probably a letter too small. That’s worth fixing. A review of 18 studies found that between 63% and 72% of the people studied were wearing shoes that didn’t match the length or width of their feet, and poor fit was linked with foot pain, corns and calluses.2 Most of those studies looked at older adults, but the lesson holds for everyone: fit is worth two minutes with a tape measure.
Socks or no socks?
Either. The lining is soft enough to wear barefoot and plenty of people do. Others like a thin no-show sock. Neither changes your size, so don’t size up for socks.
What if I still get it wrong?
You can exchange or return within 30 days of delivery. Try them on indoors on a clean floor first, because pairs worn outside can’t come back. In the US we email you a free return label. The details are on our shipping and returns page.
