If it's 100% cotton it will shrink when you wash it and will get progressively smaller and it will shrink a lot if you wash it warm/hot. How much? Unfortunately, that part is very hard to control. Some companies prewash the fabric before they make the gi to reduce shrinkage, others don't. Sometimes it will tell you on the label/package if the fabric has been prewashed.

If you got a cotton blend like cotton polyester then you better exchange it because these will not shrink.

Also gi will feel really baggy if you are not used to wearing a gi. Trust me, you do want enough room to have a full range of motion. The gi is not supposed to help your opponent by pinning you, so you can't move as much. So be careful that you don't shrink it too much. Too many guys wear their gi too tight because it 'looks' better but then they can't even get their leg up.

Well, if you have only tried it on then you should exchange it for the proper size. If you have used it already, wash and dry with heat and it will shrink. That's about as much shrinkage as you're going to get.

Sounds like it would have to shrink more than you can possibly do. Better to return it and get the correct size. If you wash it or do anything to it the seller is not going to allow you to return it.

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I got a new Gi last night and it is comically large. Like hangs to my knees almost and my pants fall off. Not good. How can I shrink it? I've seen many things on the internet for how to shrink a Gi just a little bit. So what do I do if I want to shrink it a lot?