What's a good way to tell a person that their pants don't fit?

Question

What's a good way to tell a person that their pants don't fit?

Answer 1

tell them that their pants have reached "critical mass" without the  "m" in front of mass :P

Answer 2

Don't tell them. They probably already know. If it bothers you, just don't look at them.

Answer 3

Sugest another size (or bigger or smaller...)