Welcome to
Seam Logic.

Seam Logic is a free patternmaking guide for designing, drafting, and fitting your own garments. Each module starts with a foundational pattern block, then builds from there to introduce new patternmaking methods through a series of exercises and study projects.

Illustration of a dress form
design / draft / fit / sew

Grow your pattern design skills.
Make clothes you'll actually wear.

How to use it

A patternmaking guide you can work through at your own pace

Seam Logic is organized as a sequence of modules, skill-building inserts, and study projects. You can follow the manual in order or use individual sections as a reference while working on your own patterns.

Illustration of a measuring tape
Illustration of a notebook

Drafting

Each module introduces patternmaking concepts through paper-based and muslin-based exercises, and study projects.

Illustration of a pincushion

Fitting and testing

Muslin exercises and study projects are used to evaluate fit, proportion, mobility, and the relationship between the shape of the pattern and your body.

Illustration of a thimble

Study projects

Projects bring several concepts together and provide a place to apply new techniques in a finished garment.

Seam Logic draws from established patternmaking resources.

The guide refers you to outside patternmaking texts for drafting methods, especially Helen Joseph Armstrong's Patternmaking for Fashion Design. Seam Logic provides a structured approach for working through those methods, testing them, and applying them to your own designs.

Illustration of a seam ripper
Illustration of scissors

Current status

Seam Logic is currently in beta.

Modules will be published here one at a time as they are tested and revised. The material will continue to change as feedback is incorporated and later sections of the manual are developed.

View available modules →