Quick Answer: Most cotton gis shrink 2 to 5 percent in length over the first few hot washes, with sleeves and pants losing the most. Buy so that the jacket sleeve ends at or slightly past the wrist bone and the pants sit at the ankle bone when new — after shrinkage that lands in the legal and comfortable range. Preshrunk and ripstop fabrics move much less.

You try it on in the shop and it is perfect. Three weeks later the sleeves are at mid-forearm and a referee is looking at your wrists.

The gi did what cotton gis do. The size chart just did not mention it.

How much does a gi actually shrink?

It depends on the weave and whether it was preshrunk, and the range is wide enough to matter.

• Single weave, not preshrunk: the most movement, often 3 to 5 percent in length
• Gold and double weave: similar or slightly more, and they are heavy to begin with
• Pearl weave, preshrunk: the common modern default, usually 1 to 2 percent
• Ripstop pants: very little, often under 1 percent
• Cotton-polyester blends: minimal, but they feel different and some competitors dislike them

Shrinkage is mostly lengthwise, which is why sleeves and pant legs are the problem and the chest rarely is. It also happens fastest early — expect roughly 70 percent of the total in the first three washes, then it tapers.

Heat is the driver. A hot wash and a tumble dry will take a gi to its final size in one cycle. A cold wash and a hang dry will keep it near its original size almost indefinitely, which is a tool you can use deliberately in either direction.

What should it measure when new?

Aim for these on a brand new, unwashed gi, and let the first washes bring them in.

Jacket sleeves: ending at or just past the wrist bone with the arm extended straight. If it covers part of your hand, that is too long even accounting for shrinkage — you will be fighting the cuff on grips.

Jacket body: long enough to cover the hips comfortably with a little to spare. Jackets ride up as they shrink and a short jacket comes untucked constantly.

Pants: hem at the ankle bone, not above it. Pants shrink more than most people expect.

Chest and shoulders: should fit properly right now. Width does not shrink meaningfully, so what you feel in the shop is what you get. A tight chest will stay tight.

If you are between sizes, the general rule is size up for non-preshrunk cotton and stay true for preshrunk pearl weave.

Myth vs Fact: Gi Care and Sizing

Myth: All gis shrink the same amount. Fact: The spread runs from under 1 percent to over 5 percent depending on weave and treatment. The label matters more than the brand.

Myth: You should deliberately shrink a gi to fit. Fact: You can, and controlled hot washing is a legitimate technique — but it is one-directional and easy to overshoot. Do it in stages, one hot cycle at a time, checking between.

Myth: Hanging a gi to dry prevents all shrinkage. Fact: It prevents most of the heat-driven shrinkage, but cotton still relaxes and contracts somewhat when wet. Hang drying slows it, it does not stop it.

Fact: Gis stretch slightly during training and contract again in the wash. The size you measure straight out of the dryer is the smallest it will be all week.

Myth: A heavier gi is more durable. Fact: Weave density and stitching quality drive durability far more than raw weight, and heavy gis are miserable in a hot room.

How do you wash a gi to control the size?

Two protocols, depending on what you want.

To keep it as big as possible: cold wash, gentle cycle, hang dry away from direct heat. Turn the jacket inside out to protect the collar stitching. This is the default for a gi that fits well now.

To shrink it deliberately: hot wash, then tumble dry on medium, one cycle at a time. Measure the sleeve after each. Stop as soon as you hit the target, because there is no way back.

Either way:

• Wash after every session, without exception, and never leave it in the bag
• Skip fabric softener — it degrades the fibres and reduces grip friction
• White vinegar in the rinse handles odour better than any additive marketed for it
• Dry it fully before storing; a slightly damp gi in a closed bag is how skin problems start

That last point is not really a sizing issue but it is the one that causes actual harm, especially in warm months when mat hygiene is already under pressure.

What about competition legality?

Worth knowing before you shrink anything, because the rules are measured, not eyeballed.

Under the most common competition rulesets, the jacket sleeve must reach to within about 5 centimetres of the wrist with the arm extended, and the pants must reach to within about 5 centimetres of the ankle. There are also collar thickness and width limits, checked with a gauge at weigh-in.

The practical consequence: a gi that shrank a full size is often no longer legal, even though it still feels wearable for training. People find this out at the check-in table on the morning of a competition.

If you compete, keep a dedicated gi that gets cold washed and hang dried only, and let your daily training gi do whatever it does. Measure the competition one against the ruleset before the event rather than on the day.

FAQ: Gi Sizing Questions, Answered

I am between an A1 and A2. Which do I buy?

For preshrunk pearl weave, take the one that fits your chest and shoulders properly now. For non-preshrunk cotton, size up and shrink to fit deliberately. Width is the thing you cannot fix; length is.

My gi shrank too much. Can I get it back?

Partially. Wash cold, then stretch the wet garment lengthwise by hand and hang it to dry under its own weight. You will recover some length, rarely all of it.

Do womens cut gis shrink differently?

The fabric behaves the same, but the cut has less spare length in the jacket body to begin with, so the same percentage is more noticeable. Pay particular attention to jacket length when sizing.

How many gis do I need?

Two is the practical minimum once you are training more than twice a week, because a gi needs a full day to dry properly and training in a damp one is a skin infection risk.

TL;DR:

• Cotton gis shrink 2 to 5 percent lengthwise, most of it in the first three washes
• Buy so sleeves end at the wrist and pants at the ankle bone when new
• Heat drives shrinkage — cold wash and hang dry to hold size, hot wash in stages to reduce it
• Width does not shrink; a tight chest stays a tight chest
• Competition rules are measured, so keep a dedicated cold-washed gi if you compete

Buy for where the gi ends up rather than where it starts, wash it after every single session, and dry it fully. That is most of gi ownership, and it saves you from finding out about shrinkage at a check-in table.