How does Reiss suit sizing work?
Fact-checked 2026-09-29 · every claim links to its source below
What Reiss publishes
- The size guide sits in the help centre rather than the shop, and its blazer, shirt and trouser tables are headed "Garment Measurements" — the brand labels the kind of number it is giving, which many do not.1
- Two blazer fits are published, Slim Fit and Modern Fit, and Modern is exactly +0.5" on Slim at every size. Half an inch is the entire published difference between them at the chest.1
- A caveat before anyone uses that blazer table to pick a size: across labels 34 to 46 — twelve inches of label — the published chest moves only 43" to 49", about half an inch of chest per inch of label, and a label 34 is shown with a 43" chest. No jacket grades that way, so the figures are either a half-measure or the chart is mislabelled. It is reproduced here as "Reiss publishes this", never as a size recommendation.1
- Shirts are sized S/M/L with a collar translation and no separate sleeve length: XS 15", S 15.5", M 16", L 16.5", XL 17", XXL 17.5", 3XL 18".1
- Reiss converts collars to centimetres to one decimal — 15" = 38.1, 16" = 40.7 — rather than rounding to whole centimetres the way T.M. Lewin does. A European buyer gets a truer number but no whole-centimetre collar to match against a Continental shirt.13
- The shirt range stops at an 18" collar and starts at 15" — narrower at both ends than Charles Tyrwhitt (14–20") or T.M. Lewin (14.5–20").13
- Trousers carry a single inside leg — 32" / 82 cm — at every waist size, in both Slim and Modern. They are also keyed to the jacket chest number rather than a waist: size 34 is a 30" waist, size 46 a 41.7" waist. The implied drop is about 4, widening slightly across the range.1
- Reiss publishes no suit fit names in its editorial suit guide — that guide covers general measuring and fit principles only, with no Reiss-specific fit names, sizing advice or hemming statement. Slim and Modern exist only on the help-centre size table.21
Does it run small or large?
- No consensus. No reliable current buyer aggregation was located for Reiss suiting, and Reiss publishes no fit meter of the kind J.Crew or Banana Republic carry, so no direction is asserted here.12
- The usable substitute is the trouser fact: whatever the chest reads, budget for a hem, because there is one leg length in the range.1
| Size | Waist (garment, in) | Inside leg | Implied drop |
|---|---|---|---|
| 34 | 30 1 | 32 in 1 | ~4 |
| 36 | 31.9 1 | 32 in 1 | ~4 |
| 38 | 33.9 1 | 32 in 1 | ~4 |
| 40 | 35.8 1 | 32 in 1 | ~4 |
| 42 | 37.8 1 | 32 in 1 | ~4 |
| 44 | 39.7 1 | 32 in 1 | ~4 |
| 46 | 41.7 1 | 32 in 1 | ~4.3 |
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Questions people ask
Are Reiss measurements body or garment?
Garment — the tables are headed "Garment Measurements" 1. You subtract the ease yourself, as at T.M. Lewin and Moss.
What inside leg do Reiss suit trousers come in?
One: 32" / 82 cm, at every waist, in both Slim and Modern fit 1. Every buyer who is not a 32" leg is hemming.
What is the difference between Reiss Slim and Modern fit?
Half an inch of published chest at every size — Modern is Slim +0.5" 1. That is the whole documented difference, and the fit names appear only on the help-centre table, not in the editorial suit guide 2.
Can I use the Reiss blazer chest table to pick my size?
Not reliably. Across labels 34 to 46 the published chest moves only 43" to 49", and a label 34 is shown with a 43" chest 1 — no jacket grades that way, so the figures are either half-measures or mislabelled. Use the fit difference, not the absolute numbers.
Sources
What Reiss publishes
- Menswear size guide — REISS help centre, 2026-09-29brand-stated
- The Guide: Men's Suits Guide — Reiss, 2026-09-29brand-stated
- Size guides — collar ranges — T.M. Lewin, 2026-09-29brand-stated