Mathematress

The in-bed mathematics that one performs in order to calculate how many hours or minutes they will be able to sleep for if they fall asleep immediately. Usually this is done in desperation after failing multiple attempts at falling asleep. The calculations usually begin while uncomfortably lying awake and trying to force yourself to sleep, you use the time you intend to sleep by and the time you have to get up, and all time in between is the Mathematress calculated sleep time.