This running calculator tells you your per-km pace and how fast to run each round for a certain distance, letting you pace yourself.This is a _very_ bare-bones calculator.
This running calculator helps you to calculate your speed per km, given the distance you ran. It also tells you your speed for 2.4km and your IPPT points.
If you are running on a track, this app tells you how many rounds you should run, and how fast to run each round so that you achieve your desired time.