What size M&S suit am I, UK or US?
Fact-checked 2026-09-29 · every claim links to its source below
What M&S publishes
- The clearest body-versus-garment statement of any off-the-rack brand here: "Take your actual body measurements as they are more accurate than measuring over your clothes." The chart headers read "CHEST (TO FIT)" and "WAIST (TO FIT)" — the number is the body the garment is made to fit.1
- A CM / IN toggle prints both unit sets in the same table, with verbatim measuring instructions for collar, chest, waist, inside leg and jacket length ("Measure from the centre back of your neck to your hemline").1
- M&S publishes a sleeve length per chest per length variant. Read it and the actionable point falls out: the sleeve grows only 0.2" per 2" of chest within a length variant, but 1.0" per step from Short to Regular to Long to Extra Long. A 40" chest with long arms should buy 40 Long, not 42 Regular.1
- Body length is published as an explicit delta: "Short -1.4 inch/-3.5cm, Long +1.4 inch/+3.5cm, Extra long +2.8 inch/+7cm" from regular length.1
- Trousers: waist to fit from 26" to 52", with five inside legs identical at every waist — Short 29", Regular 31", Long 33", Extra Long 35", XX Long 37". They are sold to a finished inside leg, not unhemmed. That is by far the widest off-the-rack suiting grid in this set.1
- Waistcoats run XS 34 through 3XL 52 chest to fit, in Regular and Long back lengths.1
- M&S does not use EU 48/50 anywhere. On the UK site the jacket selector is two controls, Chest (36–52) and Length (Short / Regular / Long); on the US site the same controls appear with the chest options prefixed "US 34in, US 36in, US 38in…". A 40 at M&S is a 40 in New York.456
- Because length is a separate dropdown, M&S offers every chest in every length — a US retailer's 40S may simply not exist in a given cloth; at M&S it does.45
- Four fits with written definitions, and the brand asserts the order: Regular is "our loosest-fitting suit style", then Tailored ("an elegant, contemporary cut with a narrower waist"), then Slim ("a closer fit across the chest and waist"), then Skinny ("slimmer lapels, a shorter-length jacket and slim-cut trousers"). "Tailored" here means slimmer than Regular, not made-to-measure — a genuine source of confusion.6
- All four fit cards use the same fit model — "Model is 6ft1"/187cm and wears a 38R jacket and 32R trouser" — which tells you the Regular length runs generous, and that the photography is not a guide to what a 6'1" buyer should order.6
- No numeric chest-to-waist drop is published for any of the four fits; the definitions are prose and icons only. Jacket chest is published to 54", with the product pages observed running 36–52 and 36–48 by style, and no size surcharge is stated anywhere for the larger sizes.6145
Does it run small or large?
- No consensus, and no brand-stated claim. M&S publishes no runs-small meter of the kind J.Crew carries and prints no per-item flag of the kind Zara does; the suiting product pages inspected carried few reviews and their bodies did not render to a text read.15
- What can be said is more useful than a folk verdict: M&S publishes the to-fit body chest, the sleeve length and the body-length delta for every size. A buyer who measures themselves as instructed and reads the table does not need a rule of thumb.1
If you get the size wrong
- Returns run 28 days, and the clock starts at delivery: "You may return unused products within 28 days of delivery with a printed return note." The UK size guide itself advertises "Hassle free returns within 28 days."21
- UK product pages advertise "Free returns for online orders"; the US returns page requires a printed return note and does not advertise free return postage.42
- M&S US publishes no size-swap exchange flow — only "Request Return" and "Track Return". A US buyer with the wrong size returns and re-orders; there is no free exchange of the J.Crew or Zara kind.2
| Chest to fit | Short | Regular | Long | Extra Long |
|---|---|---|---|---|
| 36 in | 24.2 1 | 25.2 1 | 26.2 1 | 27.2 1 |
| 38 in | 24.4 1 | 25.4 1 | 26.4 1 | 27.4 1 |
| 40 in | 24.6 1 | 25.6 1 | 26.6 1 | 27.6 1 |
| 42 in | 24.8 1 | 25.8 1 | 26.8 1 | 27.8 1 |
| 44 in | 25 1 | 26 1 | 27 1 | 28 1 |
| 46 in | 25.2 1 | 26.2 1 | 27.2 1 | 28.1 1 |
| 48 in | 25.4 1 | 26.4 1 | 27.4 1 | 28.3 1 |
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Questions people ask
What is the EU size for an M&S 40 jacket?
There is no conversion to do — M&S sizes in inch chest on both its UK and US sites, and the US site even prefixes the options "US 38in", "US 40in" 45. A 40 at M&S is a 40 chest.
Are M&S chest numbers the body or the jacket?
Your body. The headers read "CHEST (TO FIT)" and the instruction is "Take your actual body measurements as they are more accurate than measuring over your clothes" 1.
I have long arms — should I size up at M&S?
No, go up a length instead. The sleeve grows 0.2" per 2" of chest but a full 1.0" per length step, so 40 Long beats 42 Regular for a 40" chest 1.
What is M&S Tailored fit?
A slimmer cut than Regular, not made-to-measure: M&S ranks Regular as its loosest, then Tailored, then Slim, then Skinny 6. No numeric drop is published for any of them 6.
Sources
What Marks & Spencer publishes
- Men's suits size guide — Marks & Spencer, 2026-09-29brand-stated
- Returns — Marks & Spencer US, 2026-09-29brand-stated
- Tailored Fit Pure Wool Twill Suit Jacket — size selector — Marks & Spencer UK, 2026-09-29brand-stated
- Tailored Fit Italian Wool Rich Tweed Suit Jacket — size selector — Marks & Spencer US, 2026-09-29brand-stated
- The Men's Suit Fit Guide (from the Autograph Tailored Fit jacket page) — Marks & Spencer, 2026-09-29brand-stated