Measuring yourself (body): Measure across your chest from armpit to armpit, then pick the size above your number for a loose fit.

Measuring a garment (laid flat): Lay a T-shirt that fits you on a flat surface, measure straight across from armpit to armpit, and pick the size that matches your number. No need to add anything.

Bust: wrap a tape all the way round the fullest part of your bust, level and snug.

Measured before washing, ±2cm.