Remove your gi from your gym bag as soon as possible after training, even if you are not ready to put it in the wash. The longer the gi remains wet with sweat, the harder it will be to get clean. Airing it out reduces the potential for sweat stains.
Soak your jacket and pants before running them through the wash cycle. Fill your washing machine with water and mild laundry detergent. When the detergent is dissolved, soak your karate uniform for 15 to 20 minutes. Do not wash the belt. Unless the belt has become exceptionally grimy or has come in contact with a rancid substance, it is against martial arts tradition to wash it.
Place some towels or other soft items inside the washing machine with your gi. This decreases the amount of friction the heavy canvas will create when it bounces through the wash cycle, which puts less stress on the stitching.
Run the washing machine through its complete wash cycle.
Take your gi out of the washing machine immediately after the wash cycle is complete and hang it up to dry. The wet gi should not remain in the machine for an extended period of time.