Free sleep tool

Sleep calculator: when to go to bed, when to wake up

This tool estimates bedtimes and wake-up times using fixed 90-minute blocks and your chosen time to fall asleep.

Wake-up time

To wake up at 07:00, go to bed at:

21:459h · 6 blocks of 90 min7.5–9 hours
23:157.5h · 5 blocks of 90 min7.5–9 hours
00:456h · 4 blocks of 90 min
02:154.5h · 3 blocks of 90 min

Time to fall asleep 15 min

Fifteen minutes is the standard default, not a fact about you. Set it to what your nights actually look like and every time above moves with it.

Treat these as targets with slack in them, not train departures. And knowing the time is the easy half: you still have to get up.

What is a sleep calculator?

This tool estimates bedtimes and wake-up times using fixed 90-minute blocks and your chosen time to fall asleep. It does not measure your sleep stages.

How to use it

Two modes, one number each. Pick whichever matches the situation you're actually in at the moment you're reading this.

Pick your mode
Working backward from something fixed (a flight, a shift, first period)? Use "I want to wake up at." Already in bed at midnight, negotiating with yourself? Use "I'm going to bed now" and see what the alarm can honestly be set to.
Set how long you take to fall asleep
The default is 15 minutes. If you're out before the podcast finishes, drag it down. If you lie there relitigating a conversation from 2019, drag it up. Nobody else's calculator lets you touch this, and it's the number that changes every result.
Take the closest time and commit
Pick the row that gives you the sleep you need, not the one that lets you stay up. Then actually set the alarm, and put the phone somewhere you have to stand up to reach.

Is the 90-minute sleep cycle a myth?

It's an average that got promoted to a rule. In "Normal Human Sleep: An Overview" (Principles and Practice of Sleep Medicine), Mary Carskadon and William Dement put a full cycle at 70 to 120 minutes. It shifts from person to person, and it shifts inside a single night: cycles stretch as morning gets closer, so your last one is longer than your first. Ninety minutes is the middle of that range, not a measurement of your brain.

Real sleep cycles vary within and between nights. A clock calculation cannot predict a cycle boundary or guarantee an easier awakening. There is no validated 15-minute window around these results; prioritize enough time asleep over a particular minute.

Age	Recommended sleep
Children 6–12	9 to 12 hours
Teens 13–18	8 to 10 hours
Adults 18–60	7 hours or more

AASM / SRS (2015, 18–60) · AASM (2016, 6–18): AASM / SRS 2015 · AASM 2016

The calculator can't get you out of bed

The calculator suggests times; it does not set an alarm or know whether you will sleep through it. Once you have chosen a schedule, set your alarm in the app you use.

Risly is the alarm we built for that gap. There is no snooze button anywhere in the app, and the alarm only goes quiet once you've completed one of nine missions: scan an object across the room, solve math, replay a memory pattern, scan a QR code you printed, scan the barcode off a cereal box, draw the shape it asks for, kiss your partner, shake the phone, do push-ups. It's iOS 26 and up, built on Apple's AlarmKit, so Android is out for now. And if what you want is to be eased awake, buy a sunrise lamp instead. This app is the opposite of that on purpose.

Wondering how much sleep you have already lost? Calculate your sleep debt

Frequently asked questions

How many sleep cycles do I need per night?

90 × 5 = 450 min; 90 × 6 = 540 min. For adults aged 18–60, AASM and SRS recommend at least 7 hours of sleep regularly. The hours matter more than the number of 90-minute blocks.

Is 6 hours of sleep enough?

For adults aged 18–60, AASM and SRS recommend at least 7 hours of sleep regularly. The hours matter more than the number of 90-minute blocks.

What time should I go to bed to wake up at 6am?

With 15 minutes to fall asleep, 22:15 allows 7.5 hours before 06:00; 20:45 allows 9 hours. These are time budgets, not predictions of sleep cycles.

Is the 90-minute sleep cycle real?

Why am I still tired after 8 hours of sleep?

Feeling tired after eight hours can have several causes. This calculator cannot identify them or assess sleep quality. If tiredness persists or affects daily life, discuss it with a healthcare professional.