Wool has been used for centuries to make clothes because of its durability and warmth. Sometimes, larger wool garments like coats are just too big. Fortunately, wool can be shrunk through a very simple process. Care should be taken though, because once wool has been shrunk, it can't be returned to its former size.
Examine the tag in the coat as well as the coat itself. If the coat has a lining or is made from a wool blend, then this process may not work properly or may completely ruin the coat. Make sure that the coat is 100 percent wool.
Run the coat through the washing machine. The first step in shrinking a wool coat involves water. Warm or hot water is usually best, but it's the spin cycle that does the most work.
Run the coat through the dryer on low or high heat. The combination of water and heat causes the wool fibers to shrink and bond together. Once the wool coat is dry, it should be smaller. Getting the coat to the size you want may take more than one washing.