Q and Answer: Converting European Sizes to American Sizes for Jackets and Pants
Ryan asks: Why in the hell are US sizes always exactly 10 under the Euro size. Is that totally arbitrary?
Most buyers use a quick rule of thumb when converting from European to US sizing - just subtract ten. It generally works well enough, but it isn’t actually a perfectly accurate conversion. US and European measuring systems are actually measuring slightly different things, and they’re also using different units.
American jacket sizes correspond to the circumference of the wearer’s chest. If you’ve got a 42 inch chest, then you wear a size 42. (A size 42 jacket, by the way, will usually measure about 44 inches in chest circumference because of room for motion and so forth.) Similarly, American pants sizes correspond to the circumference of the waist - a size 38 pant should have a roughly 38 inch waistband.
Traditional European sizes are slightly different.
A European size 54 jacket represents a jacket for a chest that is 108 cm around (or 54 cm across) - that’s about 42 1/2 inches. Do the same math with a size 48E and you get a chest of about 37.8 inches - almost exact. In other words, the “subtract ten” rule mostly applies, but it’s not perfect.
Pants are a little trickier. European pant sizes are based not on the waist size, but rather the hip size. A size 54 represents a man with a 108 cm circumference around the largest part of his rear. That is usually a waist of around 36 or 38 inches - much smaller than 44, of course. Generally you’ll want to add about 16 to your US size, but that varies a bit for the same reasons the jacket sizes do.
When it comes to shirts, Europe generally prefers just a single size - a neck size in centimeters. European shirts typically come with longer sleeves, which can be taken up as necessary.
Hopefully this explanation is helpful… the real rule of thumb is: TRY IT ON.

Q and Answer: Converting European Sizes to American Sizes for Jackets and Pants

Ryan asks: Why in the hell are US sizes always exactly 10 under the Euro size. Is that totally arbitrary?

Most buyers use a quick rule of thumb when converting from European to US sizing - just subtract ten. It generally works well enough, but it isn’t actually a perfectly accurate conversion. US and European measuring systems are actually measuring slightly different things, and they’re also using different units.

American jacket sizes correspond to the circumference of the wearer’s chest. If you’ve got a 42 inch chest, then you wear a size 42. (A size 42 jacket, by the way, will usually measure about 44 inches in chest circumference because of room for motion and so forth.) Similarly, American pants sizes correspond to the circumference of the waist - a size 38 pant should have a roughly 38 inch waistband.

Traditional European sizes are slightly different.

A European size 54 jacket represents a jacket for a chest that is 108 cm around (or 54 cm across) - that’s about 42 1/2 inches. Do the same math with a size 48E and you get a chest of about 37.8 inches - almost exact. In other words, the “subtract ten” rule mostly applies, but it’s not perfect.

Pants are a little trickier. European pant sizes are based not on the waist size, but rather the hip size. A size 54 represents a man with a 108 cm circumference around the largest part of his rear. That is usually a waist of around 36 or 38 inches - much smaller than 44, of course. Generally you’ll want to add about 16 to your US size, but that varies a bit for the same reasons the jacket sizes do.

When it comes to shirts, Europe generally prefers just a single size - a neck size in centimeters. European shirts typically come with longer sleeves, which can be taken up as necessary.

Hopefully this explanation is helpful… the real rule of thumb is: TRY IT ON.