Heads come in all shapes and sizes. So do hats. Unfortunately, the size of a hat doesn't always match the size of the head you want to put it on. If your hat is made of cotton, you're not completely out of luck. You can shrink your cotton hats and make them fit like they're made for your head.
How to Shrink Cotton Hats
Things You'll Need
Wash your hat, either by hand or in the washing machine. Hot water helps to shrink clothing, but it can also cause dark colors to bleed and fade. Use cold water for dark hats or hats with both dark and light colors. However, if you own a light-colored hat, it may benefit from extra shrinkage by washing it in hot water.
Put your hat in your dryer on the hottest setting, either on a drying rack or on tumble dry. The tumbling action aids in shrinkage, so using heat with the tumble dry setting offers the most opportunity for shrinkage.
Check your hat periodically by pulling it out of the dryer and trying it on. You don't want to shrink your hat too much, so repeat this step until your hat fits as desired.
Dryers tend to overheat clothing. So, if you pull your hat out before the cool-down cycle, give it a minute to cool off before handling it.