The Foundations of Sizing equips crochet and knitwear designers with the technical knowledge and tools to create garments that fit accurately across sizes and body shapes. Covering essential and secondary measurements, ease, shaping, grading, and pattern adjustments, it provides a structured, step-by-step framework for translating numbers into stitches. Designed for both hobbyists and professional designers, the book emphasizes inclusive sizing, clarity in construction, and practical application, empowering readers to move from guesswork to precision. This volume establishes the foundational skills necessary to design garments that are both wearable and well-engineered.