Short answer: most rash guards are sized by chest measurement. As a starting point, a men’s small fits a 89–94 cm (35–37 in) chest, a medium 94–102 cm (37–40 in), a large 102–109 cm (40–43 in) and an XL 109–117 cm (43–46 in). Because rash guards are cut tight, the garment itself measures smaller than your body. If you are between sizes, size up for training comfort and size down for a true compression fit.
This guide gives you men’s, women’s and kids’ rash guard size charts, explains how to measure, and shows brands and academies what to put in a rash guard spec sheet when ordering custom rash guards from a factory.
How to Measure for a Rash Guard
You need a soft tape measure and a fitted T-shirt or bare skin.
- Chest: measure around the fullest part of the chest, under the armpits, with the tape level.
- Waist: measure around your natural waist, just above the belly button.
- Height: stand straight against a wall without shoes.
- Arm length (long-sleeve rash guards): measure from the back of the neck, over the shoulder and down to the wrist bone.
Chest is the measurement that matters most. Use height and arm length to choose between two sizes.
Men’s Rash Guard Size Chart
| Size | Chest (cm) | Chest (in) | Waist (cm) | Height (cm) |
|---|---|---|---|---|
| XS | 84–89 | 33–35 | 69–74 | 160–168 |
| S | 89–94 | 35–37 | 74–79 | 165–173 |
| M | 94–102 | 37–40 | 79–86 | 170–178 |
| L | 102–109 | 40–43 | 86–94 | 175–183 |
| XL | 109–117 | 43–46 | 94–102 | 178–188 |
| 2XL | 117–124 | 46–49 | 102–109 | 180–190 |
| 3XL | 124–132 | 49–52 | 109–117 | 183–193 |
These are typical body measurements used across the fightwear industry. Each brand’s pattern is slightly different, so always check the chart of the brand you are buying from.
Women’s Rash Guard Size Chart
| Size | Bust (cm) | Bust (in) | Waist (cm) | Hips (cm) |
|---|---|---|---|---|
| XS | 76–81 | 30–32 | 61–66 | 84–89 |
| S | 81–86 | 32–34 | 66–71 | 89–94 |
| M | 86–91 | 34–36 | 71–76 | 94–99 |
| L | 91–99 | 36–39 | 76–84 | 99–107 |
| XL | 99–107 | 39–42 | 84–91 | 107–114 |
Women’s rash guards are cut with a shorter torso, narrower shoulders and more room at the bust and hips than men’s cuts. Our women’s BJJ gear buying guide covers fit differences in more detail.
Kids’ Rash Guard Size Chart
| Size | Age (approx.) | Height (cm) | Chest (cm) |
|---|---|---|---|
| YXS | 4–5 | 105–115 | 56–60 |
| YS | 6–7 | 115–125 | 60–64 |
| YM | 8–9 | 125–137 | 64–70 |
| YL | 10–11 | 137–147 | 70–76 |
| YXL | 12–14 | 147–158 | 76–82 |
Children grow fast, so most parents and academies order one size up. For gis, use our kids’ BJJ gi sizing guide.
Compression Fit vs Regular Fit
Rash guards come in two fits, and they change how you read a size chart:
| Compression fit | Regular (relaxed) fit | |
|---|---|---|
| How it feels | Skin-tight, “second skin” | Close to the body but not tight |
| Garment vs body | Garment chest is smaller than body chest, so the fabric stretches | Garment chest is close to body chest |
| Best for | No-gi competition, under a gi, grappling | Beginners, warm-ups, casual training |
| Between sizes? | Size down for compression, up for comfort | Pick the larger size |
If you train no-gi, a fit that rides up in scrambles is a problem. A silicone gripper at the hem helps keep the rash guard in place.
IBJJF Rules for No-Gi Rash Guards
If you compete in IBJJF no-gi events, the rules matter as much as the size. In summary:
- The rash guard must be elastic and skin-tight, and long enough to cover the torso down to the waistband of the shorts. Loose T-shirts are not allowed.
- Colours: black, white, or black and white, with at least 10% of your belt colour. A rash guard that is 100% your belt colour is also allowed.
- This is why many academies order ranked rash guards: one design produced in each belt colour.
- Both long-sleeve and short-sleeve rash guards are widely used in no-gi competition.
Rules change, so check the current IBJJF rule book before you compete or before you order ranked rash guards for a team.
Rash Guard Specs for Brands and Academies
If you are ordering custom rash guards from a factory rather than buying one off the shelf, a size chart is only half the job. The factory also needs a short spec sheet. These are the specs Google and buyers look for first, and what we use as standard at Onrox International:
| Spec | What to specify | Onrox standard |
|---|---|---|
| Fabric blend | Polyester/spandex ratio | 88% polyester / 12% spandex (premium 82/18 on request) |
| Fabric weight | GSM | 180–200 GSM standard, 200–220 GSM premium |
| Stretch | 2-way or 4-way | 4-way stretch |
| Seams | Stitch type | Flatlock stitching on all seams |
| Printing | Method | Full dye-sublimation, seam to seam |
| Hem | Gripper or plain | Silicone gripper optional |
| Sleeves | Length | Long, short or sleeveless |
| Fit | Compression or regular | Both available |
| MOQ | Pieces per design | 25 pieces per design, sizes can be mixed |
| Samples | Lead time | 7–10 days |
| Production | Lead time | 25–35 days after sample approval |
Higher GSM fabric feels more solid and holds compression better, while lighter fabric is cooler in hot gyms. For BJJ and MMA, 180–220 GSM is a good working range.
Garment Measurement Points for a Rash Guard Tech Pack
Body charts tell a customer which size to buy. Factories work from finished garment measurements, measured flat, for each size. Your tech pack should list these points of measure:
| Point of measure | How it is measured |
|---|---|
| Body length | High point of shoulder to hem |
| Chest width | 2.5 cm below armpit, side to side, laid flat |
| Waist width | Narrowest point, laid flat |
| Hem width | Bottom edge, relaxed, laid flat |
| Sleeve length | Shoulder seam to cuff |
| Bicep width | 2.5 cm below armpit, laid flat |
| Cuff opening | Relaxed, laid flat |
| Neck width | Seam to seam |
Add a tolerance to each point, usually plus or minus 1 cm on lengths and widths. Our tech pack guide explains how to set one up.
How to Size a Team or Academy Order
Most academy orders go wrong on the size split, not the design. A simple way to plan it:
- Collect real measurements from members with a shared form, rather than asking for “usual T-shirt size”.
- Order a size set first. Ask the factory for one sample in each key size (for example S, M, L, XL) and let members try them on.
- Use a typical split if you have no data. For adult men’s academy orders, M, L and XL usually make up most of the order, with fewer S and 2XL.
- Keep a small buffer of the most common sizes for new members. Ordering matching shorts too? Use our grappling shorts size chart.
Common Rash Guard Sizing Mistakes
| Mistake | What happens | Fix |
|---|---|---|
| Ordering by T-shirt size | Rash guards feel too tight or too loose | Measure the chest |
| Ignoring the fit type | A compression cut feels a size small | Check whether the chart is compression or regular |
| No gripper on no-gi tops | Rash guard rides up in scrambles | Add a silicone hem gripper |
| One chart for men and women | Poor fit at bust, hips and shoulders | Use a separate women’s pattern |
| Washing hot | Fabric loses stretch and prints fade | Wash cold, air dry |
Frequently Asked Questions — Rash Guard Sizing
Q: Should a rash guard be tight or loose?
A: Tight. A rash guard should sit close to the skin so it does not bunch, catch fingers or ride up. A compression rash guard is tighter still. If it restricts breathing or leaves deep marks, go up a size.
Q: Do rash guards shrink?
A: Polyester/spandex rash guards hardly shrink. Heat is the bigger risk: hot washes and tumble dryers damage spandex and make a rash guard lose its stretch. Wash cold and air dry.
Q: What GSM is best for a BJJ rash guard?
A: Around 180–220 GSM works for most BJJ and MMA training. Lighter fabric is cooler; heavier fabric feels more solid and holds compression better.
Q: Are rash guard sizes the same as T-shirt sizes?
A: Not exactly. A rash guard in your T-shirt size often feels tighter, because it is cut to sit against the body. Measure your chest and use the brand’s chart.
Q: What is the minimum order for custom rash guards?
A: At Onrox International the minimum is 25 pieces per design, and you can mix sizes and long or short sleeves within that quantity.
Q: How long does it take to make custom rash guards?
A: Our samples take 7–10 days and bulk production takes 25–35 days after you approve the sample, plus shipping.
Order Custom Rash Guards from Onrox
Onrox International makes custom sublimated rash guards, ranked rash guards and matching spats for BJJ academies, MMA teams and fightwear brands in Sialkot, Pakistan. Send us your logo, colours and size split and we will reply with a free digital mockup and a factory-direct quote.
Custom BJJ Rashguards → | Rash Guard Manufacturer in Pakistan → | Request a Quote →
Related guide: ordering matching spats? See our BJJ spats size chart.