What time should I go to bed?
Work backwards from when you need to wake, or forwards from going to bed now, in cycles of about 90 minutes plus a little time to fall asleep.
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How this works
Sleep often comes in cycles of about 90 minutes. Waking near the end of a cycle can feel easier than waking from a deeper stretch in the middle. This calculator adds about 15 minutes to fall asleep, then counts 4, 5 or 6 cycles.
Five and 6 cycles — roughly 7.5 to 9 hours in bed, plus that fall-asleep buffer — are marked for most adults. Four cycles is a shorter night, useful when the morning is fixed and you are going to bed late, not a target to repeat.
These are starting points. Real cycles vary, and they change across the night. If you are not sleepy at the earlier bedtime, wait for sleepiness rather than forcing the clock. If a time leaves you groggy, try the neighbouring option for a week and notice.
This does not diagnose insomnia or tell you how much sleep you "should" get. It is a way to pick a first bedtime or wake time to experiment with.
Questions people ask
- Are sleep cycles really 90 minutes?
- About 90 minutes is a common average. Yours may run shorter or longer, and later cycles are often lighter. That is why the times are starting points.
- Why add 15 minutes to fall asleep?
- Most people take a little while to drop off. About 15 minutes is a gentle buffer so the cycle count starts from sleep, not from lights out.
- What if I am not sleepy at the suggested bedtime?
- Stay up until you feel sleepy, and keep the wake time steady. Going to bed because the clock said so is how a lot of people end up lying awake.
This tool is educational, not medical advice, diagnosis or treatment. Persistent or severe sleep problems deserve a qualified medical assessment.