Yarn conversion - including thread conversion - is the problem of picking yarns that are equivalent to the ones specified in a pattern, usually from a palette of yarns offered by a different brand.

Often the yarn tyrants do everything to prevent their customers from converting to another yarn, whereas yarn pirates frequently publish conversion tables.

Regular conversion tables allow only relative color mapping between pairs of yarn manufacturers and are often highly unreliable. Whenever possible you should rely on absolute color tables that provide the color of the yarn in relation to some color space such as Pantone Tables or CIELAB tables.

The Open Yarn Database is an open and free database providing support for yarn conversion based on absolute color tables

• Official conversion tables
• Inofficial conversion tables
• Chained conversion tables

released by yarn manufacturers:

• Ginnie Thompson
• Eterna
• Jan Lynn
• Kreinik
• Presencia USA

released by yarn stores:

• Yarntree
• Purple Kitty Yarns
• The Rocking Horse

released by crafters:

• Cyberstitchers