Men's Tailored Suit & Jacket Sizing (Chest & Drop)
Direct Answer
Men's tailored suit jackets and sport coats are sized by chest circumference in even inches (e.g., 38, 40, 42) combined with a height-based length classification: Short (S, ≤5'7"), Regular (R, 5'8"–5'11"), Long (L, 6'0"–6'3"), and Extra Long (XL, >6'3"). Standard pre-nested suit packages incorporate the classic 'Drop 6' rule to pair jacket size with trouser waist.
Source: IAF (International Apparel Federation) / ASTM D6960
Specs
| Governing Standards | IAF Standards / ASTM D6960 / Savile Row Tailoring Codes |
| Chest Size Range | 36 to 48 in even 2-inch increments (e.g., 36, 38, 40, 42, 44, 46, 48) |
| Short (S) Height Bracket | 5'4" to 5'7" (163–170 cm) | Jacket back length ~28.5"–29.5" (72–75 cm) |
| Regular (R) Height Bracket | 5'8" to 5'11" (173–180 cm) | Jacket back length ~30.0"–31.0" (76–79 cm) |
| Long (L) Height Bracket | 6'0" to 6'3" (183–190 cm) | Jacket back length ~31.5"–32.5" (80–83 cm) |
| Extra Long (XL) Height | >6'3" (190+ cm) | Jacket back length ≥33.0" (84+ cm) |
| Standard Suit 'Drop 6' Rule | Trouser Waist = Jacket Size - 6 inches (e.g., 40R jacket comes with 34W trousers) |
| European Drop Scale | Drop 8 (Athletic / V-Taper) | Drop 6 (Regular) | Drop 4 (Portly / Relaxed) |
Chest Measurement and Built-in Tailoring Ease
The numerical suit size corresponds directly to the actual bare chest circumference in inches. When building a Size 40 jacket, the pattern maker builds in $2.0\text{ to } 3.0\text{ inches}$ of structural ease, yielding a finished jacket chest circumference of $42.0\text{ to } 43.0\text{ inches}$. This allows uninhibited arm movement, deep breathing, and comfortable buttoning over a dress shirt and vest.
Understanding the 'Drop' (Jacket vs Trouser Ratio)
In pre-nested two-piece suits, the Drop represents the mathematical difference between the jacket chest size and the matching trouser waist: $$\text{Trouser Waist} = \text{Jacket Size} - \text{Drop}$$
- Standard Drop 6 (North America & UK): A Size $40\text{R}$ jacket is paired with $34\text{W}$ trousers ($40 - 6 = 34$).
- Athletic Drop 8 (European / Slim Fit): A Size $40\text{R}$ jacket is paired with $32\text{W}$ trousers ($40 - 8 = 32$) for lean, broad-shouldered builds.
- Drop 4 (Executive / Portly): A Size $40\text{R}$ jacket is paired with $36\text{W}$ trousers ($40 - 4 = 36$).