Measurements on each product page are taken with the garment laid flat and are given in centimetres. Compare them with something you already own that fits well — that is more reliable than a letter size.
Where a product runs large or small, we say so on its page and suggest which way to go if you are between sizes.
Still unsure? Email us with your usual size and a measurement or two, and we will tell you honestly which size to pick. We would rather get it right first time than process a return.