Cotton is a natural fabric that shrinks when it is first washed and dried. If you have cotton sweaters that are too large, they can be shrunk to fit you better. This is not a foolproof plan, however, for it is difficult to tell exactly how much a cotton sweater will shrink after it is washed. If the cotton sweater was worn and washed by another owner previously it will probably not shrink to a smaller size than it currently is.
Place the cotton sweater in the washing machine and add a small amount of detergent.
Turn the washing machine to a normal cycle with hot water. Use warm water if you are worried about the colours of the sweater fading.
Remove the sweater from the washing machine after the cycle has finished. Place the sweater in the dryer.
Dry the sweater until it is completely dry on the hottest dryer setting. Remove the sweater from the dryer.