Sleep Cycle Calculator

Work out the best times to go to bed or wake up so you rise between sleep cycles feeling refreshed, not groggy.

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How to use the Sleep

Choose a mode: I must wake at…, I'll sleep at…, or Sleep now.
Enter the relevant time (skip this for Sleep now), and adjust the cycle length and fall-asleep time if you like.
Read the recommended times — each shows the number of sleep cycles, total hours and a quality rating.
Pick a time that gives you 5–6 complete cycles to wake up refreshed.

Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.

About Sleep

How sleep cycles work

Sleep runs in cycles of roughly 90 minutes, moving through light, deep and REM stages. Waking at the end of a cycle leaves you refreshed; waking mid-cycle leaves you groggy. Most people need 5–6 cycles (about 7.5–9 hours) a night.

Three ways to use it

Enter the time you must wake up to get ideal bedtimes, enter a bedtime to get ideal wake-up times, or choose 'Sleep now' to see when to set your alarm if you fall asleep right away.

More accurate than most

Unlike basic bedtime calculators, this one lets you adjust the cycle length (85–100 minutes) and your personal fall-asleep time, and it labels each option with cycle count, total sleep hours and a quality rating.

Frequently asked questions

How many sleep cycles do I need?

Most adults feel best with 5–6 complete cycles, roughly 7.5–9 hours of sleep.

Why include fall-asleep time?

It takes the average person about 15 minutes to drift off, so the calculator adds this so your alarm lands at the end of a cycle.

Can I change the cycle length?

Yes — 90 minutes is typical, but you can set 85 or 100 minutes to match your own pattern.

Is this medical advice?

No — it's a helpful guide. If you regularly wake unrefreshed, consider speaking to a doctor.