How to Measure Your Head for a Cap

You've found a cap you like. You click on size and it says: "one size fits all." But you know what one size really means. It fits most heads — just not yours. So before you order something and end up returning it, you need one number: your head circumference in centimetres. The whole thing takes two minutes. And it'll save you a lot of frustration and pointless trips to the post office.

This guide walks you through measuring step by step, explains what your number means on a cap size chart, and helps you decide if you're right on the border between two sizes.

What you'll need

Best option: a soft fabric tape measure — the kind you'd find in a sewing kit (or in that drawer where random things end up). Quick and accurate.

Don't have one? No problem. A piece of string, a shoelace, a phone charger cable — anything flexible works. Wrap it around your head, mark where it overlaps, then measure the flat piece against a ruler.

Leave the metal retractable tape measure in the toolbox. It doesn't bend around a head and you'll get a useless number.

Measuring step by step

1. Stand in front of a mirror. Or ask someone to help — slightly more accurate that way.

2. Wrap the tape around your head. Run it about one centimetre above your ears, across the widest part of your forehead. Right where a cap would naturally sit. Important — the tape needs to go level all the way around, not angled up at the back.

3. Get the tension right. Not tight, not loose. Try slipping one finger between the tape and your head — one finger should fit. Three fingers? Too loose. No fingers? Too tight.

4. Read the number. Where the tape overlaps, check the centimetres. Using string? Mark the overlap with a pen, lay the string flat on a table, and measure with a ruler.

5. Measure again. Your head isn't a perfect sphere — it has shape, contours, bumps. Take two measurements and use the larger number. Better to have a millimetre more than less.

One more thing: measure with dry hair and your usual hairstyle. After a shower or with a hairstyle you wouldn't normally wear under a cap, you'll get a different number — and then wonder why.

What your number means — size chart

Head circumference (cm)	Size
54–56	S/M — standard
56–58	M/L — standard
58–59	L — standard
60–63	XL — Head of Wonder ✓
63–65+	XXL

In plain English:

Under 58 cm — standard caps will fit you. You don't need us. And that's perfectly fine.

58–59 cm — grey zone. Some regular caps still close on the last notch. Some don't. If you're tired of gambling, try XL — the comfort is on another level.

60–63 cm — you're home. Standard "one size" caps either won't close, or they'll sit on top of your head like a beanie on a basketball. Maybe you've been there — strap maxed out, cap riding high, forehead imprint after an hour. That's not your fault. That's the wrong size. Head of Wonder XL caps are engineered for exactly this range — centred on 61 cm, comfortable from 60 to 63 cm.

63 cm and above — that's XXL territory. Beyond our current range, but good to know where you fall.

For the full conversion chart and FAQ, check our size guide.

Right on the border? Here's what to do

59–60 cm: Try XL. A cap with an adjustable strap can tighten down to 59 cm — and the difference in comfort compared to a standard cap on its last notch is massive. A little room is always better than a little squeeze.

63 cm: You're at the upper edge of XL. Our caps will fit, but it may be a bit snug. Depends on head shape and cap style — a metal buckle gives smooth adjustment, a snapback has fixed steps. Worth a try.

General rule: When in doubt, go up. A slightly loose cap is comfortable. A slightly tight cap hurts. And an adjustable closure always takes up the slack.

Head shape — the other thing that matters

Circumference is the key number. But it's not the only one. How a cap looks and feels when you put it on also depends on the shape of your head.

Round head: Structured caps — baseball caps, snapbacks — visually elongate the shape. A firm crown adds a bit of definition.

Oval or oblong head: Dad hat. The soft crown follows your head's natural contours instead of forcing it into a shape it doesn't have.

Not sure what you are? Start with a baseball cap. It suits almost everyone and is the safest first pick. For a detailed rundown of all five cap styles for big heads, read our guide: Best caps for big heads in 2026.

Two minutes and you're sorted

One number. Two minutes. And no more guessing whether that cap will fit or end up in a drawer. This simple step saves you returns, complaints, and that moment in front of the mirror where you think "wrong again."

Got 60–63 cm? Then you know where to go. Browse the full Head of Wonder XL cap and beanie collection — and find the one that actually fits. Whenever you need to double-check sizing, our complete size guide is there for you.