A rashguard that is too big gives your training partner something to grab. One that is too small restricts your breathing and shoulder mobility. Sizing is one of those things that is easy to get right - if you know what to look for.
How a rashguard should fit
A properly fitted BJJ rashguard is tight to the body without restricting movement. Think compression - like a second skin. The fabric should sit flat against your chest and back with no visible bunching or loose panels.
Run a quick test: raise both arms above your head and rotate your shoulders in a full circle. If the rashguard rides up and exposes your midriff, it is too small. If you can grab the fabric with two fingers and pull it away from your body, it is too big.
How to measure correctly
Two measurements matter: chest circumference and body weight. Fightwear brands use both because body composition matters - a 90kg lean athlete and a 90kg stockier athlete need different fits.
- Measure your chest at the widest point (usually nipple line), keeping the tape level.
- Note your current weight in kg.
- Match both to the brand size chart. If they point to different sizes - lean athletes go by chest, stockier builds go by weight.
Competition fit vs training fit
| Competition | Daily Training | |
|---|---|---|
| Sizing | Size down | True size or up one |
| Fit feel | Very tight compression | Snug but comfortable |
| Fabric grip | Zero grippable fabric | Minimal |
| After washing | Wash cold to maintain fit | Stays consistent |
Common sizing mistakes
- Buying your t-shirt size: Rashguards run significantly tighter than everyday tops. A medium t-shirt wearer often needs a large or XL rashguard in performance fits.
- Ignoring weight and going by height alone: Height does not determine torso width. Chest measurement plus weight is the accurate combination.
- Assuming it will loosen: Quality rashguards maintain compression over time with cold washing. If it is tight in the shoulders when new, it will remain tight.
Senshi Blue BJJ Rashguard
IBJJF Legal · Detailed size chart on product page · €49.99
Still unsure? Contact us with your measurements and we will advise you directly.
View with Size ChartFrequently asked questions
My rashguard feels tight in the armpits - is it the wrong size or wrong fit?
Tightness in the armpit is usually a size issue. Try sizing up. A quality rashguard should have zero restriction when both arms are raised overhead.
How do I know if a rashguard fits correctly for competition?
Stand in front of a mirror and hold both arms out at shoulder height. The rashguard should sit flat with no bunching, no riding up and no visible loose panels. Then raise both arms - it should stay fully tucked.
Will my rashguard shrink after washing?
Slightly, if washed hot. Washing cold (as recommended for all fightwear) maintains the original fit. Never tumble dry - heat breaks down the spandex fibres and permanently changes the compression.
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