Loading the interactive tool… It runs in your browser — if it doesn't appear, enable JavaScript.
Waking at the end of a sleep cycle feels dramatically better than being yanked out of the middle of one — which is why 7.5 hours of sleep can leave you sharper than 8. Enter your wake-up time and get bedtimes that fit whole 90-minute cycles (plus the ~15 minutes most adults take to fall asleep), or hit "going to bed now" for the alarm times that respect your cycles.
Frequently asked questions
Why 90-minute cycles?
A full pass through light, deep and REM sleep takes roughly 90 minutes, and the lightest stage — the easy place to wake — comes at the boundaries. Ninety minutes is an average; your cycles may run 80–110, so treat the times as good targets rather than physics.
How many cycles do I actually need?
Five to six (7.5–9 hours) for most adults. Consistently four or fewer builds sleep debt no clever timing can cancel — cycle alignment optimises a good night, it doesn't replace one.
What if I take longer than 15 minutes to fall asleep?
Shift bedtime earlier by your personal lag. Regularly taking 30+ minutes is worth examining: caffeine after noon, screens at full brightness, or an inconsistent schedule are the usual suspects.