How to tell when my combat level is going to go up on runescape?

dose anyone no how to tell when my combat lvl is about to go up like when my combat is going to lvl up

Go to runehq.com and click on calulators then click combat lv then that will tell you how many more lvs you need to get a combat lv.

I think it goes up with every three defense, strength, or attack levels. Like if you gain three levels in either one, or in any combination of the three.