Hat Size Converter
Turn a head measurement into US fitted hat size (in eighths) and metric hat size.
US hat size
7 1/8
- Metric hat size
- 57
- Head circumference
- 57 cm · 22.44 in
Between sizes? Go up — a snug band or sizing tape can take up a little room.
Show the work
Head in inches
in = cm ÷ 2.54
57 ÷ 2.54 = 22.4409 in
US size, to the nearest ⅛
size = circumference ÷ π
22.4409 ÷ π = 7 1/8
How it works
US hat size = head circumference in inches ÷ π, to the nearest ⅛; metric size = circumference in cm
Questions
- How does the hat size converter work?
- US hat size = head circumference in inches ÷ π, to the nearest ⅛; metric size = circumference in cm.
- What do I need to enter?
- Head circumference, Unit. Optional fields can be left blank.
Related tools
- Coffee to Water Ratio CalculatorFind grams of coffee for your water (or water for your coffee) at the SCA golden ratio or your own brew ratio.
- Baker's Percentage CalculatorTurn a dough's weights into baker's percentages and hydration — or percentages back into grams for any flour amount.
- Turkey Cooking Time CalculatorUSDA roasting time for a turkey by weight at 325 °F, stuffed or not, plus the safe internal temperature and thawing time.
- Reading Time CalculatorEstimate how long a text takes to read silently or aloud, from a word count or pasted text.
- TV Size & Viewing Distance CalculatorFind the best seating distance for a TV size — or the TV size for your couch — using the SMPTE and THX viewing-angle guidelines.
- Cat Age CalculatorConvert a cat's age to human years with the veterinary age chart, and see its life stage.
Want this on your site? Embed the hat size converter.