Apparel Size

Hat Size Converters

Convert hat sizing systems and head measurements with dedicated standard, snug, and loose fit profile pages.

Related paths

Explore this conversion collection

Use the grouped routes below to move between related directions, standards, materials or profiles within this conversion collection.

Quick start hat size converters

Start with the most common US, UK, EU, and circumference directions.

US Fitted to EU Size (Standard Fit) EU Size to US Fitted (Standard Fit) US Fitted to UK Fitted (Standard Fit) UK Fitted to US Fitted (Standard Fit) Head Circumference (cm) to US Fitted (Standard Fit) US Fitted to Head Circumference (cm) (Standard Fit) Head Circumference (in) to EU Size (Snug Fit) EU Size to Head Circumference (in) (Loose Fit)

Standard Fit hat size mirrors

Each direction below is a dedicated page with fixed fit profile context for direct reverse lookup.

US Fitted to Head Circumference (in) (Standard Fit) US Fitted to Inner Diameter (mm) (Standard Fit) UK Fitted to EU Size (Standard Fit) UK Fitted to Head Circumference (cm) (Standard Fit) UK Fitted to Head Circumference (in) (Standard Fit) UK Fitted to Inner Diameter (mm) (Standard Fit) EU Size to UK Fitted (Standard Fit) EU Size to Head Circumference (cm) (Standard Fit) EU Size to Head Circumference (in) (Standard Fit) EU Size to Inner Diameter (mm) (Standard Fit) Head Circumference (cm) to UK Fitted (Standard Fit) Head Circumference (cm) to EU Size (Standard Fit) Head Circumference (cm) to Head Circumference (in) (Standard Fit) Head Circumference (cm) to Inner Diameter (mm) (Standard Fit) Head Circumference (in) to US Fitted (Standard Fit) Head Circumference (in) to UK Fitted (Standard Fit) Head Circumference (in) to EU Size (Standard Fit) Head Circumference (in) to Head Circumference (cm) (Standard Fit) Head Circumference (in) to Inner Diameter (mm) (Standard Fit) Inner Diameter (mm) to US Fitted (Standard Fit) Inner Diameter (mm) to UK Fitted (Standard Fit) Inner Diameter (mm) to EU Size (Standard Fit) Inner Diameter (mm) to Head Circumference (cm) (Standard Fit) Inner Diameter (mm) to Head Circumference (in) (Standard Fit)

Snug Fit hat size mirrors

Each direction below is a dedicated page with fixed fit profile context for direct reverse lookup.

US Fitted to UK Fitted (Snug Fit) US Fitted to EU Size (Snug Fit) US Fitted to Head Circumference (cm) (Snug Fit) US Fitted to Head Circumference (in) (Snug Fit) US Fitted to Inner Diameter (mm) (Snug Fit) UK Fitted to US Fitted (Snug Fit) UK Fitted to EU Size (Snug Fit) UK Fitted to Head Circumference (cm) (Snug Fit) UK Fitted to Head Circumference (in) (Snug Fit) UK Fitted to Inner Diameter (mm) (Snug Fit) EU Size to US Fitted (Snug Fit) EU Size to UK Fitted (Snug Fit) EU Size to Head Circumference (cm) (Snug Fit) EU Size to Head Circumference (in) (Snug Fit) EU Size to Inner Diameter (mm) (Snug Fit) Head Circumference (cm) to US Fitted (Snug Fit) Head Circumference (cm) to UK Fitted (Snug Fit) Head Circumference (cm) to EU Size (Snug Fit) Head Circumference (cm) to Head Circumference (in) (Snug Fit) Head Circumference (cm) to Inner Diameter (mm) (Snug Fit) Head Circumference (in) to US Fitted (Snug Fit) Head Circumference (in) to UK Fitted (Snug Fit) Head Circumference (in) to Head Circumference (cm) (Snug Fit) Head Circumference (in) to Inner Diameter (mm) (Snug Fit) Inner Diameter (mm) to US Fitted (Snug Fit) Inner Diameter (mm) to UK Fitted (Snug Fit) Inner Diameter (mm) to EU Size (Snug Fit) Inner Diameter (mm) to Head Circumference (cm) (Snug Fit) Inner Diameter (mm) to Head Circumference (in) (Snug Fit)

Loose Fit hat size mirrors

Each direction below is a dedicated page with fixed fit profile context for direct reverse lookup.

US Fitted to UK Fitted (Loose Fit) US Fitted to EU Size (Loose Fit) US Fitted to Head Circumference (cm) (Loose Fit) US Fitted to Head Circumference (in) (Loose Fit) US Fitted to Inner Diameter (mm) (Loose Fit) UK Fitted to US Fitted (Loose Fit) UK Fitted to EU Size (Loose Fit) UK Fitted to Head Circumference (cm) (Loose Fit) UK Fitted to Head Circumference (in) (Loose Fit) UK Fitted to Inner Diameter (mm) (Loose Fit) EU Size to US Fitted (Loose Fit) EU Size to UK Fitted (Loose Fit) EU Size to Head Circumference (cm) (Loose Fit) EU Size to Inner Diameter (mm) (Loose Fit) Head Circumference (cm) to US Fitted (Loose Fit) Head Circumference (cm) to UK Fitted (Loose Fit) Head Circumference (cm) to EU Size (Loose Fit) Head Circumference (cm) to Head Circumference (in) (Loose Fit) Head Circumference (cm) to Inner Diameter (mm) (Loose Fit) Head Circumference (in) to US Fitted (Loose Fit) Head Circumference (in) to UK Fitted (Loose Fit) Head Circumference (in) to EU Size (Loose Fit) Head Circumference (in) to Head Circumference (cm) (Loose Fit) Head Circumference (in) to Inner Diameter (mm) (Loose Fit) Inner Diameter (mm) to US Fitted (Loose Fit) Inner Diameter (mm) to UK Fitted (Loose Fit) Inner Diameter (mm) to EU Size (Loose Fit) Inner Diameter (mm) to Head Circumference (cm) (Loose Fit) Inner Diameter (mm) to Head Circumference (in) (Loose Fit)

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 documentation

Explanation

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.

This Hat Size family groups leaf pages that share one direction-specific model for reproducible output.

Every linked leaf keeps one explicit conversion model so quick references and full calculations remain aligned.

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.

Are reverse directions available?

Yes. Every direction has a dedicated mirror page using the same fit profile.