Since the imperial system is a crazy system with numbers that don't add up if you want to convert it, its time for everyone to get acquainted with the metric system.
Why? Because it's much easier. It's all dividable in 10. 10mm is 1cm, 10cm is 1dm, 10dm is 1m.. and so on.
I can't believe that a lot of people like the imperial system better. Cuz like 12 inches go into 1 foot. How does that makes sense?
Here's a guide on howto do the metric system. Read it, and learn!