How to measure for a suit jacket

A suit jacket is sized by the chest. The trousers are sized by the waist. Ruban Size's suits template puts it in one line: "Jacket sizes follow your chest; trousers follow your waist." Everything else you measure (shoulders, sleeve, length) checks that the jacket of your chest size also fits the rest of you.

How to measure for a suit jacket, step by step

A second person makes this quicker and more accurate, especially for the shoulders.

1. Wear a thin dress shirt. No sweater, no jacket, nothing in the shirt pocket.
2. Chest. Arms down, pass the tape under the arms, around the fullest part of the chest and across the shoulder blades. Keep it level, breathe out normally and read. This is your jacket size measurement.
3. Waist, for the trousers. Around the line where your trousers sit, over the shirt, tape level.
4. Shoulders. Across the back, from the outer point of one shoulder bone to the other, following the curve of the back.
5. Sleeve. From the shoulder point, down the outside of the arm with the elbow slightly bent, to the wrist bone.
6. Back length. From the base of the collar at the back of the neck, straight down to where you want the jacket to end. A classic jacket covers the seat.
7. Height, barefoot. Brands use it to pick between short, regular and long.

The chest and sleeve steps are the same as for a shirt; how to measure shoulder width and sleeve length has the details and the usual mistakes.

Or measure a jacket that fits

Lay it flat, buttoned, front up, and measure:

• Chest: straight across from armpit to armpit, then double it.
• Shoulders: from one shoulder seam to the other, across the back.
• Sleeve: from the shoulder seam to the edge of the cuff.
• Back length: from the seam under the collar to the hem, down the middle of the back.

Compare these with the brand's garment measurements, not with its body chart. A jacket is always larger than the chest inside it.

Suit sizes: the number and the letter

In the US and the UK, a jacket size is a number close to the chest in inches, plus a letter for the length: 40S, 40R, 40L are the same chest in a short, regular and long cut. In Europe, the number is close to half the chest in centimeters. The Men's suits and blazers template shows both, ten apart:

Two things to read in it. First, a UK/US 40 on this chart fits a chest of 98 to 101 cm, which is 38.6 to 39.8 in: the "chest in inches" rule is close, not exact, so check the brand's chart. Every system side by side is in men's clothing sizes compared.

Second, the drop. Each size pairs a chest with a waist 14 cm smaller, about 5½ in: a 40 jacket goes with a 33 to 34 in waist. Suits sold as a set have a fixed drop. If your waist is further from your chest than that, look for suit separates, where jacket and trousers are bought in their own sizes.

Common mistakes

• Measuring over a sweater or a jacket.
• Arms raised or chest puffed out while you read.
• Choosing the jacket by the trouser waist. The waist only decides the trousers.
• Taking your chest in inches as the size without reading the chart.
• A straight arm for the sleeve, or measuring to the thumb.
• Ignoring the shoulders. A tailor can shorten sleeves and take in a waist; shoulders that are too narrow or too wide are much harder to fix.

What it means for a Shopify store

• Jackets by chest, trousers by waist. One chart can hold both, as the template does, or each product gets its own.
• Lengths with numbers. S, R and L mean nothing without the back length and sleeve length of each, or the heights they're cut for.
• Garment measurements in their own tab: chest laid flat, shoulders, sleeve, back length.
• The drop, if suits are only sold as sets.
• A fit note. The template's reads "Tailored cut: if you prefer room to layer, take one size up."

How Ruban Size handles suit jackets

In the suits template, the EU and UK / US columns are marked as size systems: shoppers switch between them above the table, and the guide remembers their choice. Chest and waist convert between cm and in. The How to measure block has a chest and a waist step, and each lights up its line in the body figure and its row in the table.

Find my size reads the chart as "Jackets, blazers and suits". The chest counts most; the waist only refines the answer near a boundary. A 100 cm chest with an 86 cm waist gets "Your size: 50", both lines in the middle of the 50 range. The same chest with a 92 cm waist reads "You are between 50 and 52. We suggest 50.", with "Waist 92 cm: 54, bottom of the range" and "52 may also fit if you like more room." The chest still decides.

"Fit I like" moves the answer on a body chart by half the gap between jacket ease values. A 97.5 cm chest falls between the 48 and 50 ranges: Regular reads "You are between 48 and 50. We suggest 50.", Snug gives 48.

When the chart gives the jacket's own measurements, Find my size adds jacket ease: 10.2, 12.9 or 20.2 cm for Snug, Regular and Loose, the midpoints of the Vogue, Butterick and McCall's allowances for jackets (3¾ to 4¼, 4⅜ to 5¾ and 5⅞ to 10 in). Take a blazer chart with "Chest, laid flat (cm)" at 52, 54, 56, 58 and 60 for sizes 46 to 54, which Find my size doubles to 104 to 120. A 100 cm chest plus 12.9 cm is 112.9 cm: "You are between 50 and 52. We suggest 50." With Loose, 120.2 cm: 54.

A chart titled "Tuxedos" doesn't name a garment type Find my size knows. Pick "Jackets, blazers and suits" under "Garment type" in the chart's Fit tab, and every setting above applies.

Questions

What size suit jacket am I?

Measure your chest over a thin shirt, under the arms, and find it on the brand's chart. In US and UK sizes the number is close to your chest in inches; on the Ruban Size template, a 98 to 101 cm chest is a 40, or EU 50.

What do S, R and L mean on a suit jacket?

Short, regular and long: the same chest with a shorter or longer body and sleeves. Brands give the heights or the back lengths each one is cut for.

What is the drop of a suit?

The difference between the jacket size and the trouser waist, in inches. On the template, each jacket pairs with a waist about 5½ in (14 cm) smaller than its chest.

Should I measure my chest over a shirt for a suit?

Yes, over a thin dress shirt, the way you'll wear the jacket. Not over a sweater.