Carhartt brand clothing is known for it's rugged designs and heavy material. Shrinking a Carhartt coat can be done in a similar fashion to shrinking any other cotton piece of clothing, however care needs to be taken to prevent damage to the coat itself. The company recommends ordering their coats a size up from their normal size. This is to allow for layering under the coat, but it can also allow for shrinking the coat without fear of shrinking it too much.
Check the label inside the coat before washing or drying the coat, and check the Carhartt FAQs website on cleaning and drying (see Resources). You should thoroughly understand the advice before shrinking the coat yourself.
Place the coat inside the washer. Wash the coat alone (never with other articles of clothing) and according to the instructions within the coat. Some Carhartt coats may require gentle cycles. Many Carhartt coats need to be cleaned in warm water, not hot.
Remove the coat from the washer when the cleaning cycle is complete. Place the coat in the dryer (again, by itself) and set the dryer temperature to warm to shrink the garment. Hot can damage the non-cotton parts of the coat. However, certain Carhartt jackets are treated with flame-resistant coatings and cannot be dried on warm or hot. They need to be dried on low. Double-check the information on your coat on the Carhartt FAQs website.
Set the dryer to warm, or to tumble dry low if the coat is flame resistant. For the low setting, simply run the dryer for a longer period of time.
Take the coat out of the dryer every 15 minutes or so to gauge how much the coat has shrunk. Do not run the dryer for a whole cycle or two cycles without checking the coat. Try the coat on after removing it from the dryer every 15 minutes or so. When the coat is at the desired size, do not put the coat back into the dryer.