 How to Shrink a Sweatshirt If you bought a sweatshirt and later realized it's too big, don't worry. You can easily shrink your fabrics or your sweatshirt fits better. Try submerging your sweatshirt in hot and or boiling water, and use a hot heat setting to launder your garment. If your shirt is not shrunk enough after using the washer and dryer, run an iron over top of a wet sweatshirt. With either method, you may be able to shrink your sweatshirt to your liking. Using the washer and dryer. Check the tag to review washing instructions and material type. View the tag on your shirt to see if the garment has any specific washing instructions. Some fabrics easily shrink with heat, while some fabric will not shrink at all. If the tag tells you to wash your garment in cool water, you can wash it in warm water to shrink it. For example, cotton easily shrinks, as does cotton and polyester blends. Synthetic fabric like rayon and nylon do not shrink. For example, cotton easily shrinks, as does cotton and polyester blends.Synthetic fabric like rayon and nylon do not shrink. Wash your sweatshirt in hot water as a first attempt to shrink it. To do this, put your sweatshirt in a clean sink, and run hot water over the garment for 5-10 minutes. Let the sweatshirt cool down to room temperature, and then check the sizing. If you are satisfied with the amount your sweatshirt shrinks, you can launder it as normal. If you want to shrink your sweatshirt even more, use boiling water, your washing machine, and or your dryer. To check the size, hold the shirt up to your torso and examine it in the mirror. Submerge your cotton sweatshirt in boiling water to shrink the fabric. If your sweatshirt did not shrink enough after using hot water, boil a large pot of water on high heat. When your water comes to a boil, submerge your garments, put a lid on the pot, and turn off the heat. The boiling water helps shrink your shirt even more. If you want to shrink your shirt even more, use boiling water as a first attempt to shrink the fabric. If you are satisfied with the amount your sweatshirt shrinks, you can launder it as normal. If you want to shrink your sweatshirt even more, use boiling water, your washing machine, and or your dryer, to check the size, hold the shirt up to your torso and turn off the heat. If you want to shrink your shirt one size, leave it in the water for 10 to 15 minutes. If you hope to shrink your shirt two sizes, let it cool to room temperature. Do not do this if washing a polyester sweatshirt. The high temperatures can make the fabric rough or stiff. Polyester should not be heated above 178 degrees Fahrenheit 81 degrees Celsius. Alternatively, put your sweatshirt in your sink and pour boiling water over top the garment. Then, let it cool to room temperature. If you want to shrink your shirt one size, leave it in the water for 10 to 15 minutes. If you hope to shrink your shirt two sizes, let it cool to room temperature. Do not do this if washing a polyester sweatshirt. The high temperatures can make the fabric rough or stiff. Polyester should not be heated above 178 degrees Fahrenheit 81 degrees Celsius. Alternatively, put your sweatshirt in your sink and pour boiling water over top the garment. Then, let it cool to room temperature. Select the hot water setting on your machine after applying hot water. After you've soaked your sweatshirt in hot and or boiling water, put it in your washing machine. You can wash your sweatshirt with other garments you want to shrink, such as T-shirts. Select the appropriate load size, and pour in one cap full of laundry detergent. After you wash your sweatshirt, check the sizing before you put it in the dryer.ss equals, reference, aria label equals, link to reference 4, greater than to maximize your shrinkage, use the longest washing size. If you just want to shrink it one size, you can use a normal wash cycle. If you are washing a small load of laundry, you only need one half of a cap of detergent, then checking the size, hold the wet sweatshirt in front of your torso and eyeball the size in the mirror. Once the sweatshirt is dry, you can try it on to check the fit. Put your sweatshirt in the dryer on the hottest heat setting. If your sweatshirt is still not your desired size, use a very warm heat setting on the longest drying time. This can shrink your sweatshirt an additional size. If your sweatshirt is shrunk to your liking, follow the drying directions on your garment tag. Most list a medium heat setting and normal drying time. Check the fit of your sweatshirt after it cools to room temperature. After the dryer cycle is complete, take out your sweatshirt and lay it on a flat surface. Once your sweatshirt is at room temperature, put it in to check your overall fit. If your sweatshirt did not shrink adequately, try using an iron to shrink it another size. If your sweatshirt did not shrink adequately, try using an iron to shrink it another size.