Sleep Calculator

Fall asleep on time tonight

Play brown noise in the BRW app and set its sleep timer. It plays offline with the screen off.

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How the Sleep Calculator Works

You do not sleep in one long, even block. You go through sleep cycles: from light sleep, to deep sleep, to dream sleep, and back again. On average, one cycle takes about 90 minutes. Most adults go through four to six of them in a night.

At the end of a cycle, sleep is lighter. Many people find it easier to wake up then than in the middle of deep sleep, when an alarm can leave you groggy. So the calculator works in whole cycles.

It also adds the time it takes you to fall asleep. The usual figure is about 15 minutes. If you are often awake for longer, change it in the calculator.

An example. You want to wake up at 7:00 am. Six cycles is 9 hours, and five cycles is 7.5 hours. Add 15 minutes to fall asleep. So the best bedtimes are about 9:45 pm and 11:15 pm.

How Much Sleep Do You Need?

The calculator marks 5 and 6 cycles as best because they give an adult 7.5 or 9 hours. That fits the advice from the CDC, the US public health agency:

Source: CDC, “About Sleep” [1]. Younger children need more, often with naps.

How Exact Is It?

Use the times as a guide, not a rule. 90 minutes is an average. Real cycles are often shorter or longer, about 80 to 120 minutes, and they change through the night [2]. Your own cycles can also change from night to night.

So if you wake up a little before or after the time, that is normal. What matters most is that you get enough sleep, at about the same times each day.

If you often sleep 7 hours or more and still wake up tired, or you snore loudly, talk to a doctor. A calculator cannot find a sleep problem.

Tips to Fall Asleep at Your Bedtime

Keep the same times. Go to bed and get up at about the same time every day, also at the weekend. This helps your body know when to feel sleepy.

Make the room dark, cool and quiet. Put the phone face down, or in another room.

Cover sudden noises. A car door, a neighbour or a snoring partner can wake you. A steady sound, such as brown noise, makes these sounds stand out less. Research on noise as a sleep aid is mixed, so try it and see if it helps you [3].

Let a timer turn the sound off. In the BRW app, you can set a sleep timer, so the sound stops after you fall asleep. Not sure how loud your room is? Check it with the decibel meter.

How Long Should a Nap Be?

Choose Nap in the calculator. It gives two alarm times:

A power nap of about 20 minutes. It is short enough that you usually do not go into deep sleep, so it is easier to wake up from.

A full cycle of about 90 minutes. It lets you go through deep sleep and come back to light sleep before the alarm.

Avoid long naps late in the day. They can make it harder to fall asleep at night.

References

1. About Sleep: How much sleep do I need? Centers for Disease Control and Prevention (CDC). cdc.gov/sleep/about
2. Stages of Sleep. Sleep Foundation. sleepfoundation.org/stages-of-sleep
3. Riedy SM, Smith MG, Rocha S, Basner M. Noise as a sleep aid: A systematic review. Sleep Medicine Reviews. 2021;55:101385. doi:10.1016/j.smrv.2020.101385 · PubMed 33007706

Frequently Asked Questions

Related pages

• Baby Sleep Calculator — A bedtime for your baby or toddler, from the CDC sleep hours by age.
• Brown Noise — The deepest colour: a steady rumble that is best for traffic noise and long nights.
• Brown Noise App — Which brown noise app to install, whether it is really free, and what an app can do that a browser tab cannot.
• Block Out Snoring — Snoring is the hardest sound to cover: deep, uneven, and a metre from your head with no wall in the way. What really helps.
• Decibel Meter — Check how loud your room is, and which noise colour covers it best.
• Pomodoro Timer — A free focus timer: 25-minute rounds and breaks, with brown noise built in.
• Sound Masking — Masking does not block sound. It raises the background so the noise stops standing out, and the colour has to match the noise.