What is the minimum spec for rotors before they need to be replaced?

I have the following:

RF: 819
LF: 834
RR: 340
LR: 325

I was also told I have torn caliper boots. They suggested I replaced the calipers.

What do you think? I have 82k on a '95 maxima.

 

Dang, and i just got mine turned but i forgot what they said

They measured mine in inches.

 

Buy a rebuilding kit for your calipers and replace the boots yourself.