Getting the size right is one of the most critical aspects of professional hatmaking. Whether you’re crafting a custom piece or producing a collection, understanding how to measure, convert, and work with standard hat sizes ensures a perfect fit and customer satisfaction. In this guide, we’ll walk through the key measurement systems, conversion tips, and useful tools for accurate hat sizing.

The Basics: Circumference First

Hat sizes are based on the head circumference, typically measured in centimeters or inches. To take an accurate measurement:

• Use a flexible tailor’s measuring tape.
• Place it around the widest part of the head (just above the ears and across the forehead).
• Ensure it sits comfortably—not too tight, not too loose.
• Record the measurement precisely.

International Hat Size Conversions

Different regions use different systems. Here’s a quick reference:

📝 Tip: Always confirm which sizing system your customer or market uses.

Tools for Accurate Sizing

Professional hatmakers often rely on these tools:

• Size rings or blocks: Wooden rings in fixed sizes for consistent shaping.
• Conformateur: For measuring complex head shapes.
• Formillion (or conformer): Used to transfer head shape to a block.
• Hat sizing tape: Helps adjust slightly larger hats for a snug fit.

Working With Size Gradation

If you’re building a size range (e.g., S, M, L), it’s common to:

• Use nested blocks or interchangeable sizing rings for flexibility in production.
• Increase or decrease 2 cm in head circumference between each size.

Mastering hat sizing is key to delivering hats that not only look great, but feel perfect to wear. Understanding measurement systems, using the right tools, and building with precision will elevate your craftsmanship and reduce returns or adjustments.