Jacket Size Calculator with Layering Room
This jacket size calculator builds in the inch of layering room most calculators forget. Enter your shirt-on chest measurement and the tool returns the right jacket size for layering over a shirt or sweater — without you doing the math. Works for blazers, sport coats, denim jackets, and casual outerwear in US, UK, EU sizing. Use the calculator below to get your exact fit in 30 seconds.
How it works
Measure yourself
Take your bust, waist, and hips with a soft tape. See the full measurement guide.
Enter the numbers
Type your measurements into the calculator above. Pick inches or cm — the tool converts both ways.
Get your size
Match the result against the brand's chart and order with confidence.
Men's tops — chest-driven sizing
| Size | US | UK | EU | Chest |
|---|---|---|---|---|
| XS | 34 | 34 | 44 | 32–34" |
| S | 36 | 36 | 46 | 35–37" |
| M | 38–40 | 38–40 | 48–50 | 38–40" |
| L | 41–43 | 41–43 | 52–54 | 41–43" |
| XL | 44–46 | 44–46 | 56–58 | 44–46" |
| XXL | 47–49 | 47–49 | 60–62 | 47–49" |
Frequently Asked Questions
Should I size up for a jacket if I plan to layer underneath?
The calculator already adds a layering allowance. If you'll wear a heavy sweater under it (winter wool layer), size up by 1 additional.
How do I measure my chest for a jacket?
Wear the shirt or sweater you'd typically layer under the jacket. Measure around the fullest part of your chest, tape parallel to the floor, snug not tight.
What's the difference between a blazer and jacket size?
Blazers are sized like suit jackets (36, 38, 40 — chest in inches). Casual jackets often use S/M/L. Same body, different label conventions.
Should I size up for an oversized blazer trend?
Yes — go up 1 from the calculator's recommendation for the relaxed shoulder-drop look that's been on-trend.
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