A numerical size is not a universal measurement. It can vary by brand, cut and style. Start with the information on the product page rather than a number you wear elsewhere.
Compare with a garment that fits
Lay a similarly shaped garment flat. Measure its width below the armholes, length and, where useful, sleeves, waist or hips. A flat width is not a body circumference, so compare measurements taken in the same way.
Account for the cut
Fitted, straight and roomy garments will not drape in the same way even when their dimensions are similar. Consider how you will wear the piece too: a jacket layered over knitwear needs more room than a top worn on its own.
DixOnze sizing
Sizing is stated for each garment. Most of the catalogue uses soft one-size, while some structured pieces are offered from S to XL. This does not establish one universal numerical range for every style.
Read the size guide, then check the selector and details on the product page. If a useful measurement is missing, use the contact page and include the product reference.