what is the size that mens suits and sport jackets start at?

Question

I mean boys sizes seem to end at size 20, but nobody seems to know what chest size, arm length, heighth etc makes up the smallest of the mens size line.

Answer 1

That's because each manufacturer is different. Store A's men's 20 might be 20 inches, and Store B might be 21 inches.

It works the same way for women's clothing. A Size 0 may actually be a Size 4, but they put 0 on the tag because it sounds better to women.

Just have to ask the person in the store, or measure it out yourself.