How does the bedtime calculator work?

Enter the time you need to wake up. The calculator works backwards in 90-minute sleep cycles and accounts for an average 14-minute sleep onset (time to fall asleep). It returns four bedtime options — 6, 5, 4, and 3 full cycles — so you can pick the one that matches your sleep need.

What time should I go to bed to wake up at 7am?

To wake up at 7:00 AM after 5 complete sleep cycles (7.5 hours), go to bed at 11:16 PM. For 6 cycles (9 hours), aim for 9:46 PM. For 4 cycles (6 hours), aim for 12:46 AM. These times assume a 14-minute sleep onset.

A complete adult sleep cycle — light sleep, deep sleep, and REM — takes roughly 90 minutes on average. Waking at the end of a cycle, rather than in the middle of deep sleep, dramatically reduces sleep inertia and helps you feel alert on waking.

Bedtime Calculator

Enter the time you need to wake up. We'll calculate the best times to fall asleep based on your natural 90-minute sleep cycles — so you stop fighting your alarm.

Ideal bedtime scene with a person settling into bed and an alarm clock showing the recommended hour

💤 Quick nap calculator

How bedtime is calculated

Your brain runs through roughly five to six 90-minute sleep cycles each night. Within each cycle you move from light sleep (NREM 1 & 2) into deep sleep (NREM 3) and back out to REM. Waking up mid-deep-sleep — which happens when your alarm hits at an arbitrary hour like 7:00 AM after eight hours — is what causes the grogginess, brain fog, and "I slept eight hours and still feel terrible" feeling that sends most people hunting for a better solution.

This bedtime calculator solves it by working backwards from your wake-up time in 90-minute increments, then adding the average 14 minutes it takes an adult to fall asleep. You get four options:

6 cycles / 9 hours — bonus rest, ideal when you've been under-sleeping
5 cycles / 7.5 hours — the recommended default for most adults
4 cycles / 6 hours — minimum viable, survivable short-term
3 cycles / 4.5 hours — emergency only

When bedtime calculation gets it wrong

The 90-minute figure is a population average. Your personal cycle length might be 80 minutes or 110. If you're consistently waking at the "right" time on this calculator but still feeling groggy, your natural cycle length is probably shorter or longer than average. The most reliable fix is to track when you naturally wake without an alarm over a two-week holiday — that gap tells you your real cycle length.

Also useful for shift workers

If you work nights, the same maths applies — work backwards from when you need to be at work. The biggest mistake shift workers make is sleeping exactly 8 hours; almost nobody can sustain that on a rotating schedule. Targeting 4–5 complete cycles (6–7.5 hours) at a consistent daily time is more sustainable.

Need the inverse — given a bedtime, when should I wake up? Use the wake-up calculator instead. For nap planning, see the nap calculator.