How it works
Calculate your standard US hat size from your head circumference.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
1-
?circumference=Head Circumference (cm)Number · Optional · Default: 58
Outputs
1-
resultResultText · Primary output
result contains the calculator’s complete rendered result area, including its visible result cards, tables, charts, and messages.
Find your standard hat size from your head circumference
Description
The Hat Size Calculator is a sizing utility that converts the physical circumference of your head into a standard US Hat Size (e.g., 7 1/4). While many modern hats are “One Size Fits All” or use Alpha sizing (S/M/L), high-quality fitted hats and professional headwear require a specific numerical size based on the diameter of your head.
Inputs
- Head Circumference (cm): The measurement around your head, usually taken right above the ears and across the forehead.
Outputs
- Hat Size: The standard US numerical size expressed as a whole number and fraction (e.g.,
7 1/4).
Chart
- N/A: This tool provides categorical sizing results.
“Good to Know”
- Measurement Tip: Use a flexible cloth measuring tape. If you don’t have one, use a piece of string to measure your head and then hold the string against a ruler.
- US vs. UK: US hat sizes are calculated based on the internal diameter of the hat. UK sizes are traditionally slightly different, but most global brands use the US standard.
- Fit Preference: Some people prefer a “comfortable” fit (slightly loose), while others prefer a “snug” fit. If you are exactly between two 1/8 increments, choose the size that matches your preference.
Examples
Example 1: Small Head
- Input: 56 cm
- Output: US Size: 7
Example 2: Average Adult
- Input: 58 cm
- Output: US Size: 7 1/4
Example 3: Large Head
- Input: 62 cm
- Output: US Size: 7 3/4