Jacket Size Calculator
Get your suit or sport-coat size from a tape measure. Enter your chest at its fullest point (inches or cm) and your height in feet and inches to get the numeric US size with length — like 40R — plus the alpha size (S/M/L), the EU size, and the classic drop-6 trouser match.
Example: with Chest measurement 40 · Chest unit inches · Height (feet) 5 · Height (extra inches) 10 → Jacket size: 40R (Regular, 5 ft 8 in to 5 ft 11 in).
- Alpha sizeM (chest 38-41 in)
- EU sizeEU 50
- Matching trouser waist34 in (standard 6 in drop)
Computed by the calculator below using its default values. Change any input to see your own numbers.
US jacket size = chest in inches rounded to the even size; the letter comes from height (Short, Regular, Long). EU size = US + 10; trousers classically run size − 6.
The number is your chest; the letter is your height
US jacket sizing is refreshingly literal: the number is your chest circumference in inches, taken at the fullest point under the arms with the tape level. Measure 40 inches and you wear a 40. Sizes come in even numbers, so round to the nearest even — and if you land exactly between, go up, because a tailor can take a jacket in far more easily than let it out.
The letter handles sleeve and body length. Short fits 5 ft 7 in and under, Regular covers 5 ft 8 in to 5 ft 11 in, Long runs 6 ft 0 in to 6 ft 3 in, and Extra Long picks up from 6 ft 4 in. Between a 40S and a 40R sit about an inch and a half of body and sleeve — enough to read instantly as wrong if you pick the wrong letter.
Drops, alphas, and EU numbers
Suit makers cut trousers to a standard "drop 6": a 40R suit ships with 34-inch-waist trousers. Athletic builds often need drop 7-8 (sold as separates), while fuller waists need drop 4 or less. Alpha sizes compress the same scale — 38-40 is M, 42-44 is L — and EU sizing simply adds 10 to the US number, so a 40R is an EU 50.
How it’s calculated
Jacket size = chest measurement in inches (cm ÷ 2.54 first) rounded to the nearest even number. Length letter by height: Short 5 ft 7 in and under, Regular 5 ft 8 in to 5 ft 11 in, Long 6 ft 0 in to 6 ft 3 in, Extra Long 6 ft 4 in and up — the standard US menswear chart. Alpha size: 36 = S, 38-40 = M, 42-44 = L, 46-48 = XL. EU size = US + 10. Trouser match = size − 6 (the classic drop 6).
Off-the-rack conventions — slim, athletic, and designer cuts shift these numbers, so treat the result as your starting size and let a fitting decide.
US jacket sizes at a glance
| US size | Alpha | EU | Drop-6 trouser |
|---|---|---|---|
| 36 | S | 46 | 30 in |
| 38 | M | 48 | 32 in |
| 40 | M | 50 | 34 in |
| 42 | L | 52 | 36 in |
| 44 | L | 54 | 38 in |
| 46 | XL | 56 | 40 in |
Standard US menswear sizing: number = chest in inches, EU = US + 10, trousers cut at drop 6.
Common mistakes
- Measuring over a sweater or with flexed posture — tape level under the arms, natural stance, one finger of slack.
- Ordering by T-shirt alpha size: brands stretch S/M/L wildly, but the chest number anchors every chart.
- Ignoring the length letter — a 40S and 40L differ by roughly 3 in of body and sleeve, far more visible than one chest size.
- Assuming the drop-6 trousers will fit an athletic build; drop 7-8 cuts or suit separates fix the gap.
Frequently asked questions
How do I find my jacket size?
Measure your chest at the fullest point under your arms, tape level and snug but not tight. That number in inches, rounded to the nearest even size, is your US jacket size; your height picks S, R, L, or XL.
What size jacket is a 42 chest at 6 ft 2 in?
A 42L — the chest gives the number and 6 ft 0 in to 6 ft 3 in falls in the Long range. In EU sizing that is a 52.
How do US and EU jacket sizes convert?
EU = US + 10. A US 40 is an EU 50; going the other way, subtract 10. The length letters do not translate — European sizes handle length with separate short/long variants (25s and 90s ranges).
What if I am between two sizes?
Size up and have it tailored. Taking in a chest or waist is routine alteration work; letting out more than an inch usually is not possible because of seam allowances.