How to Use the Sleep Calculator
Enter either a fixed wake-up time (to see bedtime options) or a fixed bedtime (to see wake-up options) — the calculator counts in 90-minute sleep cycles from that fixed point, plus a typical 15-minute buffer to fall asleep, and shows several cycle-aligned options rather than a single suggested time.
The Sleep Calculator works backward or forward from a fixed time point — here's how to use it either way.
Working from a fixed wake-up time
Enter your wake-up time, and the calculator shows several bedtime options, each corresponding to a different number of complete sleep cycles — typically ranging from 4 to 6 cycles (roughly 6 to 9 hours), covering the range most adults find workable.
Working from a fixed bedtime
The same tool works in reverse: enter a bedtime, and it shows several wake-up time options aligned with completed sleep cycles instead — useful when bedtime is the fixed point (for example, based on a partner's schedule) rather than a wake-up time.