What is the Jacket Size Calculator?
This calculator turns a single chest measurement into the jacket (suit, blazer, or coat) sizes used in the US/UK and across Europe. Men's tailored jackets are sized directly from chest circumference: in the US and UK the number on the label is your chest in inches, while in continental Europe it is roughly your chest in centimeters divided by two. Enter your chest measurement and the tool returns both numbering systems at once.
How to use it
Choose whether you want to enter your measurement in inches or centimeters, then type your chest circumference. To measure correctly, wrap a soft tape around the fullest part of your chest and across the shoulder blades, keeping the tape level and snug but not tight. Breathe normally. The calculator rounds to the nearest even number, because jacket sizes are almost always even (36, 38, 40, 42, and so on).
The formula explained
The US/UK size equals your chest in inches, rounded to the nearest even number. The EU size equals your chest in centimeters divided by 2, again rounded to the nearest even number. If you enter centimeters, we convert to inches using 1 in = 2.54 cm for the US/UK figure; if you enter inches we convert to centimeters for the EU figure.
$$\begin{gathered} \text{Jacket}_{US} = 2 \times \operatorname{round}\!\left(\frac{\text{Chest (in)}}{2}\right) \\[1em] \text{Jacket}_{EU} = 2 \times \operatorname{round}\!\left(\frac{\text{Chest (in)} \times 2.54}{4}\right) \end{gathered}$$
Worked example
Suppose your chest measures 40 inches. The US/UK jacket size is simply 40. Converting, \(40 \text{ in} \times 2.54 = 101.6 \text{ cm}\), and \(101.6 \div 2 = 50.8\), which rounds to an EU size of 50. So a 40-inch chest corresponds to a US/UK 40 and an EU 50.
FAQ
Do jacket sizes include short, regular, and long? Yes. The number (e.g. 40) reflects chest width; a letter such as S, R, or L indicates jacket length based on your height. This tool calculates the chest number only.
Should I size up for layering? If you plan to wear thick sweaters underneath a coat, consider going up one even size for extra room.
Is this for men or women? The chest-to-size method shown here is the standard for men's tailoring. Women's jacket sizing varies widely by brand and is usually not derived directly from chest circumference.
