Read garment measurements from a product source

Use a garment you already like

Lay it flat without stretching. Compare like with like: pit-to-pit width with pit-to-pit width, back length with back length, and sleeve construction with the same construction.

Width versus circumference

A 52 cm flat chest width is not the same statement as a 52 cm body chest. Do not double or reinterpret a number unless the source labels how it was taken.