The gi arrived. Your kid put it on. Too small. Back it goes — two-week wait, a frustrated child, and a missed first class.
Sounds familiar? It’s the single most common mistake when buying a kids BJJ gi. And it’s completely avoidable.
Kids BJJ gis don’t size like school uniforms. Age means nothing on a size label. It’s all about height and weight — matched to a K-series chart. Get those two numbers right and the gi fits. Every time.
Kids BJJ gi sizes run K000 through K4 — based on height and weight, not age. Measure your child’s height barefoot and note their training weight. Match both to the chart below. When in doubt, size up one: a little room to move beats a gi that won’t close.
- Kids gis use the K-series (K000–K4) — height + weight, never age
- Between sizes? Size up — gis settle slightly after the first wash
- A correct fit closes without pulling, and the sleeves clear the wrist
Why Age Is the Wrong Number
“He’s 7, get a K1.” Makes sense. Often wrong.
Two 7-year-olds: one stands 122 cm and weighs 25 kg. The other is 133 cm and 31 kg. Same age. Different sizes. The K-series cuts through that confusion by matching the gi to the body — not the birthday.
Here’s what you need:
- Height — feet flat on the floor, no shoes, back straight against a wall. Read it to the nearest centimetre.
- Weight — training weight, normal morning reading. Don’t overthink it.
Two numbers. That’s it.
The Stylso Kids BJJ Gi Size Chart (K-Series)
All garment dimensions below are from Stylso’s official spec — real measurements, nothing estimated.
| Size | Height | Weight | Jacket Span (A) | Jacket Length (B) | Pant Length (D) |
|---|---|---|---|---|---|
| K000 | 114–120 cm (45–47 in) | 18–23 kg (40–51 lb) | 114 cm | 55 cm | 72 cm |
| K00 | 120–127 cm (47–50 in) | 23–27 kg (51–60 lb) | 120 cm | 56 cm | 76 cm |
| K0 | 127–135 cm (50–53 in) | 27–32 kg (60–71 lb) | 126 cm | 61 cm | 79 cm |
| K1 | 135–142 cm (53–56 in) | 32–36 kg (71–79 lb) | 132 cm | 62 cm | 81 cm |
| K2 | 142–147 cm (56–58 in) | 36–41 kg (79–90 lb) | 138 cm | 65 cm | 85 cm |
| K3 | 147–155 cm (58–61 in) | 41–45 kg (90–99 lb) | 144 cm | 68 cm | 86 cm |
| K4 | 155–160 cm (61–63 in) | 45–50 kg (99–110 lb) | 159 cm | 71 cm | 91 cm |
Between sizes? Size up. Gis settle slightly after the first few washes, and kids need room for hip escapes and sprawls without the jacket pulling out. Height and weight disagree? Go with height — jacket length is what coaches check.
Shop the Stylso Kids Gi on Amazon — pearl weave, IBJJF approved, available in white, black, and blue:
The 3-Check Fit Test
Got the gi? Run this before the first class:
- Sleeve check. Have your child reach both arms straight forward. The sleeve end should sit about 5 cm (2 in) above the wrist bone — not at the palm, not mid-forearm.
- Jacket check. Arms straight up. The jacket should stay tucked at the hip. If the hem rides up above the ribs, go up a size.
- Pants check. Standing flat, the pant cuff should just clear the ankle bone — not drag, not cut off mid-shin.
All three pass? Right size. One fails? Revisit the chart and go up.
A Real Grip Drill for Day One
Here’s something your child can practise before they ever step on the mat. It’s the basic collar grip — used in BJJ, judo, and wrestling from the very first class.
Stand facing a partner (or a coat hook at about chest height). Grab the lapel with one hand: four fingers inside the fabric, thumb outside. Squeeze and pull back slightly toward the hip.
That’s it. That’s the collar grip every grappler learns first.
Why fit matters here: a too-small gi is already pulled tight just from wearing it. No slack to grip. A too-large gi has floppy lapels — hard to control. The right size gives firm, workable fabric. Good grip from rep one.
Have your child practise that grip 10 times each side while you pack their gear bag. By the time they’re on the mat, it’ll feel natural. This is the same drill used in judo to build gripping strength before any throwing technique is taught — it works at every level.
Sizing for Growth — the Smart Play
Kids grow fast. A K1 in October can feel snug by spring. Two approaches:
Buy current size: fits great now, one gi per year. Budget-friendly. Most families go this route.
Size up one: if your child’s in a growth spurt, the extra room buys 12–18 extra months. The jacket runs slightly large today but settles fast after a few washes.
Don’t size up two — that’s a safety issue. Excess fabric is something a training partner can grab in ways that limit movement and raise injury risk. One size up, max.
The Stylso kids gi washes well in cold water and holds its shape across hundreds of rolls. If you’re buying one gi for the year, pick the chart size. If you’re buying for growth, add one.
When K4 Isn’t Enough Anymore
K4 fits 155–160 cm and 45–50 kg. When a child outgrows that, it’s time for the adult A-series. Most kids make this jump between 13 and 16 — not at a fixed age, but when the body gets there.
The adult A0 fits 162–168 cm and 64–70 kg. A child who’s 160–163 cm and 50–60 kg sits between K4 and A0. In that window, most coaches recommend A0 — it runs slightly large for a few months, but it’s better than a too-tight K4.
Check out our best BJJ gi for teens guide for A0–A1 picks when your child is making the jump to adult sizes.
For a full review of the best BJJ gis for kids, including what to look for in a first gi, see our kids buyer’s guide.
Free: Printable Kids Gi Size Chart (PDF)
The chart above as a clean printable, plus a 3-check fit reminder and washing tips to keep the gi lasting all year. Enter your email and it comes straight to your inbox.
Free: Kids BJJ Gi Size Chart
The full K-series chart, 3-check fit test, and care tips — one printable page. Get it instantly.
FAQ
What size kids BJJ gi does my 5-year-old need?
Most 5-year-olds fit K000 (114–120 cm, 18–23 kg) or K00 (120–127 cm, 23–27 kg). Measure their height and weight rather than going by age — kids grow at different rates and age alone is unreliable.
Do kids BJJ gis shrink?
Stylso kids gis are pre-shrunk pearl weave, but you’ll see a small amount of settling after the first few washes. Don’t size down expecting it to shrink into shape — buy the chart size and wash cold to keep the fit stable.
What’s the difference between K-series and adult A-series?
Kids K-series gis are cut for smaller frames — shorter jacket, narrower shoulders, shorter inseam. Adult A-series starts at A0, which fits 162–168 cm. K4 fits 155–160 cm. A teen who outgrows K4 moves to A0 next.
Can my daughter use a kids BJJ gi?
Yes — Stylso K-series gis are unisex cuts. If she’s between sizes and prefers a closer fit, size down one. For comfort and movement, the standard height/weight chart works well for girls too.
How often should I replace my child’s BJJ gi?
When it fails the 3-check fit test. Most kids get 12–18 months from a well-fitted gi before a size-up is needed. Wash cold, air dry, and it’ll hold its shape all year.
My child’s height says K1 but their weight says K2 — which do I pick?
Go with height. Jacket length is what coaches and referees check, and it’s what affects movement most. If their weight is solidly in K2 range, run the 3-check fit test on K1 first — if the jacket rides up, go to K2.
Also see: Best BJJ Gi for Kids · Best BJJ Gi for Teens · BJJ Gi Size Guide (Adult A-Series)
