How to use the Suit Size
- Measure your chest at the fullest point, keeping the tape level under the arms.
- Measure your natural waist.
- Enter your height to determine short, regular or long.
- Read the jacket size, drop and international equivalents.
How the calculation works
US and UK jacket sizes equal the chest measurement in inches — a 42 fits a 42-inch chest, with ease already built into the pattern, so no allowance should be added. EU sizes are chest in centimetres divided by two, making a 42 US equal to a 52 EU. Length is set by height: short below about 5'8", regular to 6'1", long above that.
Drop is the difference between chest and trouser waist, and standard off-the-peg drop is 6 inches — a 42 jacket paired with 36 trousers. Athletic builds often need a drop of 7 or 8, which is why separates or made-to-measure suit them better than boxed suits. The one measurement that cannot be altered afterwards is the shoulder, so buy for shoulder fit and have the waist, sleeves and trousers tailored.
Jacket size (US/UK) = chest in inches ; EU = chest cm / 2 ; drop = chest − waistSource: Standard menswear sizing conventions for jacket chest sizing, length grading and drop.
Worked example
A 41-inch chest, 34-inch waist, 6'0" tall.
- Round chest to the nearest even size: 42.
- Height 6'0" falls in the regular length band.
- Drop = 42 − 34 = 8, above the standard 6.
- EU equivalent = 42 × 2.54 / 2 ≈ 52.
A 42R jacket, EU 52 — but with a drop of 8, buying separates will fit far better than a boxed suit.
Frequently asked questions
Should I add ease to my chest measurement?+
No. Jacket patterns already include it, so a 42 is cut for a 42-inch chest.
What is jacket drop?+
The inch difference between jacket chest and trouser waist. Standard is 6.
What can a tailor not fix?+
Shoulder width. Everything else — waist, sleeves, trouser length — is adjustable.
How do I convert to EU sizing?+
Multiply the US size by 2.54 and halve it, or simply add 10 as a quick approximation.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.