Bedtime Calculator

Most adults need at least seven hours of sleep, children and teenagers more. Working backwards from your alarm is the simplest way to protect that time. This calculator suggests bedtimes for your wake-up time based on roughly 90-minute sleep cycles and the time it usually takes to fall asleep, and shows the recommended amount of sleep for each age.

How much sleep do you need?

These ranges follow widely used recommendations such as those from the American Academy of Sleep Medicine and the US CDC. Individual needs vary; if you regularly feel sleepy during the day despite enough time in bed, talk to a doctor.

Sleep cycles and the 90-minute idea

Sleep moves through repeating cycles of lighter sleep, deep sleep and REM sleep, each lasting roughly 80–110 minutes, with more deep sleep early in the night and more REM sleep towards morning. Waking at the end of a cycle, when sleep is lighter, can feel easier than being woken from deep sleep. The calculator uses 90 minutes as a convenient average; because real cycles vary, a consistent schedule and enough total sleep matter more than hitting an exact cycle boundary.

Worked example

An adult who must wake at 6:30 AM and usually takes 15 minutes to fall asleep should aim to be in bed between about 9:15 PM and 11:15 PM for 7–9 hours of sleep. The cycle-based suggestions are 9:15 PM (six cycles, 9 hours), 10:45 PM (five cycles, 7.5 hours) or, on a short night, 12:15 AM (four cycles, 6 hours) — which is below the recommended amount. For a nine-year-old waking at 7:00 AM, 9–12 hours of sleep means lights out between roughly 6:45 and 9:45 PM.

Building a bedtime routine

1. Keep the same wake-up time every day, including weekends, as far as possible.
2. Start winding down 30–60 minutes before bed: dim lights, put screens away.
3. Keep the bedroom cool, dark and quiet.
4. Avoid caffeine in the afternoon and evening, and large meals late at night.
5. Get daylight in the morning, which helps set your body clock.
6. If you can’t sleep after about 20 minutes, get up and do something calm until sleepy.

Children’s bedtime routines

Children often settle more easily with a predictable sequence: bath, pyjamas, teeth, a story, lights out — in the same order each night. A picture chart helps younger children follow the steps and feel in control. Screens are best switched off well before bed, and caffeine (including in some fizzy drinks and chocolate) avoided in the evening.

Shift work and jet lag

For night shifts, the same arithmetic works with a daytime “bedtime”: if you finish work at 7 AM and need to be up at 3 PM, aim to be asleep by around 7:30–8 AM, with blackout curtains and a cool room. When crossing time zones, shifting bedtime by an hour a day before travel, and getting daylight at the right time after arrival, helps the body clock adjust faster. Keep caffeine for the start of a shift rather than the end.

Morning light and a steady wake time

The body clock responds most strongly to light. Getting outdoor daylight soon after waking and keeping the same wake time every day, even after a late night, makes it easier to feel sleepy at the planned bedtime. Sleeping in for hours at weekends shifts the clock later — sometimes called social jet lag — which is why Monday mornings feel harder.

Naps

Avoid long or late-afternoon naps if you have trouble falling asleep at night. Young children’s naps are part of their total sleep and are counted in the ranges above.

The sleep pack

The optional pack includes a two-week sleep diary, a printable children’s bedtime routine chart, a family sleep schedule planner and an Excel sleep log that calculates average sleep time and consistency. The calculator on this page is free.

Health note

This calculator is general information, not medical advice. Loud snoring, pauses in breathing, persistent insomnia or excessive daytime sleepiness can be signs of sleep disorders that benefit from medical assessment.

AI-assisted content

This page was drafted with AI assistance and reviewed by Kedop.