Tool description

The Crochet Hook Size Converter is a crochet hook size calculator that helps you convert between international crochet hook sizes and different sizing systems used around the world. Whether you need to convert crochet hook number to mm, find a US 7 crochet hook in mm, or convert crochet hook size mm to letter, this tool ensures you use the correct hook size for your project. Different regions use different sizing conventions, and this converter eliminates confusion when working with international patterns or purchasing hooks from various manufacturers.

Features

  • Three Sizing Systems: Convert between US letter sizes, Metric (mm), and UK number sizes
  • Comprehensive Size Range: Supports hooks from 2.25mm to 19mm (B/1 to S in US sizing)
  • Bidirectional Conversion: Convert crochet hook size mm to letter, letter to mm, or any system combination
  • International Crochet Hook Sizes: Access accurate conversions for US, metric, and UK sizing standards
  • Crochet Hook Size Calculator: Real-time conversion as you type or select
  • Accurate Mapping: Based on standard international crochet hook size charts
  • User-Friendly Interface: Simple dropdown selection and input

Supported Sizes

This crochet hook size calculator includes the most common international crochet hook sizes:

US Sizes (Letter/Number): B/1, C/2, D/3, E/4, F/5, G/6, 7, H/8, I/9, J/10, K/10.5, L/11, M/13, N/15, P/16, Q, S

Metric Sizes (mm): 2.25, 2.75, 3.25, 3.5, 3.75, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 8.0, 9.0, 10.0, 11.5, 15.0, 19.0

Example: US 7 crochet hook in mm = 4.5mm

UK Sizes (Number): 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, 0, 00, 000 (note: UK sizing is less commonly used today)

Use Cases

  • Following International Patterns: Convert international crochet hook sizes when using patterns from different countries
  • Converting Crochet Hook Number to MM: Quickly find the metric equivalent of US letter or UK number sizes
  • Shopping Online: Determine the correct size when purchasing hooks from international retailers
  • Pattern Writing: Provide hook size equivalents in mm, letters, and numbers for crocheters worldwide
  • Converting Crochet Hook Size MM to Letter: Find the US letter size for metric measurements
  • Yarn Label Instructions: Understand recommended hook sizes given in different systems
  • Teaching and Learning: Use this crochet hook size calculator to help students understand size equivalents
  • Inventory Management: Organize your hook collection by understanding size equivalents
  • Substitution Planning: Find alternative hook sizes when you don't have the exact size specified

What is Crochet Hook Sizing?

Crochet hooks are sized according to their diameter, but international crochet hook sizes use different naming conventions:

  • US System: Uses letters (B, C, D, etc.) and sometimes numbers, often combined (like H/8 or US 7)
  • Metric System: Uses millimeters (mm) to indicate the hook diameter - the most universal system for converting crochet hook number to mm
  • UK System: Uses numbers in reverse order (larger numbers = smaller hooks) - less common in modern patterns

The metric system is the most straightforward as it directly measures the hook's diameter. However, US sizing is very popular in American patterns, and older British patterns may still use UK sizing. This crochet hook size calculator helps you convert crochet hook size mm to letter (and vice versa) to bridge these different conventions and ensure you're using the right tool for your project. For example, if you need to know what a US 7 crochet hook in mm is, this tool instantly shows it's 4.5mm.