Hydroflask Standard Mouth Flex Cap

Getting the right size is the first step to comfort. Use this guide to choose your size and width online, or visit one of our stores for a free foot scan.

How to measure your feet at home

1. Measure at the end of the day, when your feet are largest, wearing the socks you plan to wear.
2. Stand on a sheet of paper with your heel against a wall and mark the tip of your longest toe.
3. Measure from the wall to the mark in inches or centimeters. Measure both feet and use the larger one.
4. Compare with the brand's size chart on the product page.

How a good fit should feel

• Length: about a thumb's width between your longest toe and the end of the shoe.
• Width: your foot shouldn't spill over the footbed or feel pinched at the ball of the foot.
• Heel: snug, with little or no slipping as you walk.
• Arch: the arch support should meet your arch without pressing into it.

Width guide

Shop wide width shoes.

Brand sizing notes

• European sizes (Birkenstock, Naot, Alegria, Dansko, ECCO): sized in whole European sizes. If you are between sizes, most customers size down and choose a regular width.
• Dansko clogs: should feel snug at the instep with a little heel movement as you walk; that is by design.
• OOFOS: most styles use unisex (men's) sizing. Women usually order two sizes down from their usual women's size.
• Running shoes: many runners go up a half size for long distances because feet swell.

Brand size charts are on each product page. Still unsure? Contact us and we'll help you choose, and remember returns are easy within 30 days on unworn shoes.