A jacket that fits in a shop mirror can still disagree with you at home. Knowing how to measure jacket size takes about ten minutes, a soft tape and, ideally, a second pair of hands. It removes most of the guesswork from buying outerwear online, and it makes a size chart something you can actually read rather than guess at.
What you need before you measure
Use a fabric tape, not a metal one, and stand naturally with your arms relaxed. Wear a thin layer, a T-shirt or a fine knit, because that is what will sit closest to the jacket. Measure over the same layer every time, and write each number down as you go. Measuring over a thick sweater will push your numbers up and leave you with a jacket that is too large the moment you take the sweater off.
How to measure jacket size: the four numbers that matter
Chest. Wrap the tape around the fullest part of your chest, just under the armpits and across the shoulder blades. Keep it level all the way round and snug enough not to slip, but not tight. This is the number most size charts are built around.
Shoulders. Measure across the back from the outer edge of one shoulder to the other, at the point where the shoulder bone ends. If a jacket is going to feel wrong, it is usually here first, because the shoulder seam cannot be altered easily.
Sleeve. With your arm slightly bent, measure from the shoulder point to the wrist bone. A jacket sleeve should finish at or just past the wrist bone, leaving a little cuff visible if you wear a shirt or knit underneath.
Length. Measure from the base of the neck, down the back, to where you want the hem to sit. Bombers sit at the waist or hip by design; blazers usually finish around mid-hip. Knowing your preferred length matters more than most people expect.
How do I know my winter jacket size? Read the chart properly
Start by checking whether a size chart lists body measurements or garment measurements. Body measurements describe you, so you match them to your own numbers. Garment measurements describe the jacket laid flat, and they are larger than your body, because the cut needs room to move. If a chart gives garment chest, compare it with your chest plus the ease you want, not with your chest alone.
Then decide on the fit you want. The Bomber Jacket is a Slim Fit through the body with easy room at the shoulder, so a chest measurement that sits close to the chart works well. A structured piece such as The Monroe Blazer has a tailored shoulder, so the shoulder number matters most and the chest can be compared more closely. For the shoulder-room question in particular, our guide to sizing a jacket up or down goes further.
Use a jacket you already own as a shortcut
The most reliable measurement is often not your body at all. Take a jacket you like the fit of, lay it flat on a bed and zip or button it. Measure straight across the chest from armpit seam to armpit seam, then double it. Measure the sleeve from the shoulder seam to the cuff, and the length from the collar seam to the hem. Compare those numbers with the garment measurements on the chart. If they line up, you have found your size in that cut. The same trick works for sweaters, and our note on how a sweater should fit shows which places to check.
Allow for what you wear underneath
Outerwear sits over other clothes, so leave room for them. A simple test: once the jacket is on, cross your arms over your chest and raise them to shoulder height. The hem should not ride far above your belt and the back should not pull tight between your shoulder blades. If you plan to wear a knit such as The Alpine Crewneck underneath, try the jacket over it, since a lightweight knit adds less bulk than it looks.
When your numbers fall between two sizes
Use the shoulder as the tiebreaker. Choose the size that fits your shoulders, because everything else is more forgiving. If you layer heavily, take the larger chest size. If you wear the jacket mostly on its own, take the smaller. For women's outerwear such as The Solis Jacket, the same logic applies, and the full range sits in the women's jackets collection, with the men's jackets collection alongside it.
More short answers on fit, layering and care live on our Style Answers page.