An overcoat size, despite what the tag says, will always be larger than a normal coat size. For example, if you have a coat that’s a size 32, and an overcoat that’s also a size 32, the overcoat is going to be larger (at least one size, such as a 34 size) in order to compensate for the size of the suit. The following article will elaborate a little on this explanation, as well as show you some ways on how to properly size an overcoat.
Determine your standard coat size. If you wear a coat size 36, you’ll want an overcoat size 36. The overcoats are designed to fit over heavy, thick layers of clothing and the sizes are supposed to be fitted accordingly. If you try on a coat that has the same tag size as your regular coat size, it should fit. If it doesn’t try a half-size to a size larger. This should work.
Check that the overcoat size you are purchasing fits you. Try it on. If it doesn’t fit comfortably or if you don’t have enough room to move, you’ll obviously want the next size up.
Measure yourself if you can’t seem to find an overcoat that fits properly and matches your normal coat size. If you are a size 36 in the waist and a size 40 in the shoulders, you may want to try wearing a normal 38-size coat. If no overcoat that coincides with your normal coat size, you might be wearing the wrong size.
Figure out what you’ll most often be wearing under the overcoat whether it be your business suit, your winter coat, a jacket or just your normal street clothes. This will make a difference in the size you need. If you normally wear street clothes under an overcoat, you’ll want a size that fits you snugly. If you wear your suit under this coat, it will be a little tight but it will still be proper size.
Find a chart that will estimate the overcoat size you need. Most charts will base themselves upon your normal coat size, your height and most times your weight. Find your expected size and see if that overcoat fits. If the overcoat doesn't fit, go one size bigger or smaller depending on why the coat isn’t fitting right. View an overcoat sizing chart in the Resources section.