Hat Size Converters
Convert hat sizing systems and head measurements with dedicated standard, snug, and loose fit profile pages.
Public interfaces
Machine access
Conversions in the canonical hat-size family require the registered fit parameter together with the source and target units.
Its 90 published directions use the same canonical engine through the website, JSON API, OpenAPI and WebMCP.
API & Agent documentationExplanation
Each conversion normalizes values through head circumference in millimeters and then maps to the destination system. Fit profile pages keep assumptions explicit and produce clean mirror paths for reverse queries.
Questions & answers
Frequently Asked Questions
Why include fit profiles in the URL?
Fit profile reflects how tightly a cap is intended to sit. Keeping it in the URL makes assumptions explicit.
How are conversions calculated?
Pages map source values to head circumference in millimeters, then map that circumference to the destination system.