Consider your height, build and allow for shrinkage when choosing your uniform size.

What height are you?  Below is the size chart used for Sapius martial art uniforms. 

Assuming you are of average build, use the advertised height as the maximum that will fit.  For example if you are 180cm tall, get a size 5; if you are 181cm, get a size 6.

What build are you?  If you have a heavy build, large shoulders, bust and/or waistline, go +1 in the sizing (you may have to shorten the sleeves and pant legs).  Alternatively if you are very thin (especially in the shoulders), you may need to go -1 in the sizing.

How much should I allow for shrinkage?  Generally poly-cotton with shrink 3-5%.  The uniform will feel slightly oversized when you wear it for the first few times.  Our uniforms have been designed to cater for shrinkage.

When trying on a uniform ALWAYS wear it properly, with your belt on, thinking about how much it will shrink, before deciding if it fits!