Hat Size Calculator
Find your perfect hat size by entering your head circumference measurement. This calculator converts your measurement to US, UK, and EU hat sizes plus the generic letter size (S, M, L, XL) used by most casual hat brands.
To measure your head for a hat, wrap a flexible tape measure around the widest part of your head, about one inch above your ears and eyebrows. Keep the tape snug but not tight. If you do not have a tape measure, use a string and then measure the string with a ruler.
- US/UK hat size = Head circumference (inches) / pi (3.14159)
- EU hat size = Head circumference in centimeters (rounded)
- Generic sizes are based on standard circumference ranges
Most adults have a head circumference between 21 and 24 inches (53-61 cm). The most common men's hat size is 7 1/4 (Medium-Large), while the most common women's size is 7 (Medium). If you are between sizes, round up for a more comfortable fit, as hats can always be adjusted tighter with sizing tape but cannot be stretched significantly.
Keep in mind that hat sizing can vary between brands and styles. Fitted baseball caps, fedoras, and dress hats follow the numerical sizing system, while beanies, bucket hats, and casual caps typically use S/M/L/XL.