Buying a suit online is easy enough, but buying one that fits well and looks good is a little more complicated. Though tailoring is an art, it's also a science of sorts with endless variables and numbers to input and weigh up. Ordering a suit without measurements is like driving blindfolded. The simplest way of finding yours is to measure an existing suit that you like the fit of. Most retailers have instructions for how they measure their garments, but in any case these are the general rules: Chest: Lay the jacket flat with all buttons closed and run a measuring tape from armpit to armpit. If you don't have a jacket that fits well, have someone measure around the broadest part of your chest (usually around nipple height), under your arms and level with the ground. Keep a finger between the tape and your body to allow for comfort. Waist: Take a pair of trousers that fit well (jeans or chinos will work just fine) and lay them completely flat. Measure the waistband from edge to edge, and double the result to get your waist measurement. Otherwise, wrap the tape around the part of your body where your waistband usually sits. Inseam: Lay a pair of existing trousers flat and measure the distance from the fork of the trousers (where both legs meet) to the hem. If you don't have a pair with the right inseam, stand straight-legged and measure the inside of your leg from your groin to where you want your trousers to end (between your ankle and the top of your shoe sole).