☾ SleepCalculator.live
Free sleep calculator

Wake up feeling more refreshed.

Pick when you want to wake up and we'll calculate suggested bedtimes using approximate sleep cycles.

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What time do you want to wake up?

Choose your wake-up time.

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or
Going to bed now? Find the best times to wake up.
Advanced options

90 minutes is a planning estimate, not an exact biological rule.

✓ No account ✓ Free ✓ Runs in your browser
Sleep cycle calculator

What time should I go to sleep?

Choose the time you need to wake up. SleepCalculator.live works backward using an approximate sleep-cycle length and your selected time-to-fall-asleep estimate.

1

Pick a time

Enter when you want to wake up, or calculate from the current time.

2

We calculate

The calculator estimates several sleep-cycle combinations.

3

Choose your schedule

Compare the suggested times and choose one that gives you sufficient sleep.

Better context

Sleep cycles are not exactly 90 minutes

Ninety minutes is commonly used as a convenient planning estimate. In real sleep, cycle length can vary across people and throughout the night.

80–100 min A useful approximate range for a sleep cycle.
4–6 cycles People commonly pass through several cycles during a night's sleep.
7+ hours Many adults need at least seven hours of sleep.

General educational information only. Sleep needs vary with age, health and individual circumstances.

More sleep tools

Need a more specific calculation?

Keep the main calculator simple, or open a focused tool when you need more control.

🌙 Bedtime Calculator Start with a wake-up time. ☀ Wake-Up Calculator Start with your bedtime. ◌ Sleep Cycle Calculator See 1–6 cycle completion times. ＋ All Sleep Tools Naps, duration, age and more.
Questions

Sleep calculator FAQ

How does this sleep calculator work?

It adds or subtracts estimated sleep cycles from your selected time and also allows for an estimated period to fall asleep.

Are sleep cycles exactly 90 minutes?

No. Ninety minutes is only an approximation. Real sleep cycles can be shorter or longer, which is why the advanced settings allow you to adjust the estimate.

Should I always choose the time with the most cycles?

In general, adequate total sleep matters. The calculator gives planning options rather than medical advice or a guarantee about how refreshed you will feel.

Does the calculator store my sleep schedule?

The main calculations run locally in your browser and do not require an account.