Start with the uncomfortable fact: there is no standard.
There is no British Standard for menswear sizing. No legal definition of a medium. Every brand decides for itself, which is why a medium from one label fits perfectly and a medium from another is unwearable. The letter on the label tells you what the brand thought, not what the garment is.
Which means the only reliable way to buy a jacket online is to work in centimetres.
The best method: measure a jacket you already own
Forget measuring your chest for a moment. Measure a jacket you own and like the fit of. It already contains every decision — your body, plus the ease you actually want, plus the layers you actually wear.
Lay it flat on a table, zipped, and smooth it out. Then measure across, not around.
- Chest — 2.5cm below the armhole, straight across from edge to edge
- Waist — 40cm down from the highest point of the shoulder seam, straight across
- Shoulder — seam to seam, across the back
- Sleeve — shoulder seam to the end of the cuff
- Length — highest point of the shoulder, straight down to the hem
Write them down. Those five numbers will buy you a jacket that fits from anyone who publishes theirs.
Flat, half-body — what that means
Nearly all garment measurements are given flat and half-body. You measure across one face of a garment lying flat, so a chest figure of 56cm describes a garment with 112cm of circumference.
This trips people up constantly. If a size chart says 56cm chest and your own chest measures 100cm, that is not too small — it is 12cm of ease, which is about right for a leather jacket worn over a shirt.
Rough guide to ease: add 8–12cm to your body chest measurement for a jacket you will wear over a shirt or light knit. Add 14–18cm if you want to layer a jumper underneath. Less than 6cm and you will feel it across the back when you reach forward.
If you do not have a jacket to measure
Measure yourself, standing relaxed, with a soft tape:
- Chest — around the fullest part, under the arms, tape level
- Waist — around your natural waist, not your trouser line
- Shoulder — from the bone at the edge of one shoulder to the other, across the back
- Sleeve — from that shoulder bone, down a slightly bent arm, to the wrist bone
Then add the ease above to the chest figure and compare to a garment chart. Do not ask someone else to guess your size — get a second person to hold the tape, because measuring your own back accurately is close to impossible.
What to do if you are between sizes
Take the larger size and shorten the sleeve.
Sleeve length is the easiest thing to alter and the most common thing to be wrong. Chest and shoulder are not — a jacket that is tight across the shoulders cannot be fixed, and one that binds when you reach forward will hang in a wardrobe unworn.
Sizing down and hoping the leather stretches is the single most common mistake. Leather does relax slightly with wear, mostly at the elbows and across the back, but it does not gain a size. A jacket that is tight when new is tight forever.
The two measurements most often wrong
In our experience, and in the complaints you will find under every leather jacket sold online, two things go wrong far more than anything else:
Sleeves too short. Very common on men over about 6ft, and on anyone with a long reach relative to their chest.
Body too short. Almost universal on cropped and café racer cuts, which are shorter than people expect. If a jacket ends above your belt when standing, it will ride up considerably when you sit or reach.
Both are worth checking against a garment chart before you order, because both are fixable at the point of ordering and irritating afterwards.
If you are being measured for made to measure
A full made-to-measure jacket usually needs around twelve measurements: chest, natural waist, hips or hem line, shoulder width, sleeve length from shoulder, sleeve length from centre back neck, bicep, wrist, neck, centre back length, front length and height.
Have someone else take them. Wear a t-shirt, not a jumper. Stand normally rather than holding yourself straight — you will be wearing the jacket as you actually stand, not as you stand for a photograph.
And when the numbers come back for confirmation, read them properly. It is far easier to correct a figure on an email than a jacket that has been cut.
Every IVY FLAG jacket publishes its garment measurements by size, and sleeve and body length can be adjusted by 3cm either way at no charge. See the size guide.