how big is 5 mm
Best Answer: 1.) --- 2.) --------------- 1 is 5 millimeters 2 is an inch.5 millimeters = 0.196850394 inch (not actual size, but scale is right.).Source(s): Richard M Â· 7 years ago. Thumbs up.eport Abuse. I needed to know how long 5 mm is, I found a perfect visual that everyone knows, the end of a pencil eraser (standard pencil, unused eraser) is 5 mm.