About the Jacket Size Calculator
This calculator applies the standard US/UK men's jacket and suit sizing convention. A jacket size has two parts: a number derived from your chest circumference, and a length letter (Short, Regular, or Long) derived from your height. It also reports the chest-to-waist "drop," which determines whether a regular, athletic, or classic cut will fit best, and converts your size to the equivalent EU number.
The formula
- Size number: measure your chest circumference (around the fullest part of your chest, over a light shirt, arms relaxed) in inches, then round to the nearest even number. Retail suits and sport coats are almost always sold in even sizes — 36, 38, 40, 42, 44, and so on.
- Length letter: based on height — Short (S) below about 5'7" (67 in), Regular (R) from about 5'7" to 6'1" (67-73 in), and Long (L) above about 6'1" (73 in). This is the widely used convention from major suit and formalwear retailers; some brands also offer an Extra Long (XL) for heights above about 6'4".
- Drop: chest measurement minus waist measurement, in inches. A 6-inch drop is the traditional "regular" cut used in most off-the-rack suits. A 7-8 inch drop is a slimmer "athletic" or modern cut, and a drop of about 4 inches or less is a fuller "classic" or "portly" cut.
- EU size: continental European sizes commonly run 10 higher than the matching US/UK number (US/UK 40 ≈ EU 50), since UK sizing uses the same chest-inch numbers as the US.
How to measure yourself
- Use a soft tape measure, wear a light shirt (not a bulky sweater), and keep your arms relaxed at your sides.
- Chest: wrap the tape around the fullest part of your chest and under your arms, keeping the tape level and snug but not tight.
- Waist: measure around your natural waistline, roughly at belly-button height, not where you wear your pants.
- Height: measure barefoot, standing straight against a wall.
Practical context
This convention gives a reliable starting point, but jacket sizing varies somewhat by brand and country, and shoulder width, sleeve length, and personal fit preference are not captured by chest and height alone. Always try a jacket on, or check a specific brand's size chart, before buying — especially for tailored or fitted styles.
Frequently Asked Questions
How is jacket size calculated?
Standard US/UK jacket sizing uses two numbers: your chest circumference rounded to the nearest even inch (36, 38, 40, 42, and so on) becomes the size number, and your height maps to a length letter — Short, Regular, or Long. A 40 inch chest with an average height gives a size of 40R.
What does the letter after my size mean, like the R in 42R?
The letter is the length fit based on your height. Short (S) generally fits under about 5 feet 7 inches, Regular (R) fits about 5 feet 7 inches to 6 feet 1 inch, and Long (L) fits over about 6 feet 1 inch. It adjusts sleeve and jacket body length, not the chest width.
What is a suit or jacket drop?
The drop is the difference in inches between your chest and waist measurements. Off-the-rack suits are traditionally cut with a 6 inch drop (regular fit). A larger drop of 7 to 8 inches is a slimmer athletic cut, while a smaller drop of around 4 inches is a fuller classic or portly cut.
How do US jacket sizes compare to EU sizes?
UK jacket sizes use the same chest-inch numbering as US sizes, so a US 40R is also a UK 40R. Continental European sizes commonly run 10 higher than the US/UK number, so a US/UK size 40 is roughly a EU size 50.