Sleep calculator: when should I go to bed?

Bedtimes for common wake-up times

If it takes you about 15 minutes to fall asleep, these bedtimes give you 6, 5 or 4 full sleep cycles before your alarm.

How the sleep calculator works

Through the night your brain moves through light sleep, deep sleep and REM sleep in repeating cycles. Each cycle lasts roughly 90 minutes on average. The calculator adds whole cycles to your sleep, plus the minutes it usually takes you to fall asleep, so that your alarm is more likely to land near the end of a cycle than in the middle of deep sleep.

Waking from deep sleep is what tends to leave you groggy for a while. Cycle-based timing is a sensible rule of thumb for avoiding that, but your cycles won't run like clockwork, and they get longer in REM toward morning. So if a time looks off by 15 minutes for you, it probably is. Adjust it.

How much sleep do adults need?

The American Academy of Sleep Medicine recommends that adults sleep 7 or more hours a night on a regular basis. That's why 5 and 6 cycles (7.5 and 9 hours) are highlighted above. Four cycles is fine for an occasional early start, not as a routine.

Individual needs vary. A better test than any calculator: if you wake without an alarm on days off and feel alert through the afternoon, you're probably close to your need.

The wake-up time matters more than the bedtime

Most people try to fix their sleep from the bedtime end. Sleep research points the other way. One of the core habits in CBT-I, the most studied non-drug approach to better sleep, is getting up at the same time every day, weekends included. A steady wake-up time anchors your body clock, and a steady body clock makes you sleepy at a more predictable time each night.

So pick the wake-up time you can keep seven days a week, then use the calculator to find the bedtime. That pair of times is what we call a sleep window.

What if you can't fall asleep at the suggested time?

Go to bed when you feel sleepy, not just because the clock says so. Lying in bed wide awake teaches your brain that bed is a place for being awake. If you're still awake after what feels like 20 minutes, get up, do something quiet in dim light, and go back when you feel sleepy. Keep the alarm where it is.

If it regularly takes you more than 30 minutes to fall asleep, or you often wake in the night and can't get back to sleep, read our guide to racing thoughts at night or waking up at 3am, and consider talking to a doctor.

A calculator gives you times. A plan keeps them.

A calculator answers tonight's question. Sleeping better over weeks depends on keeping a regular window, winding down at the same time and adjusting slowly based on how you actually slept. That's what Let Me Sleep's 6-week program is built around: it sets your sleep window from a short quiz, reminds you when to start winding down, and moves the window in small steps as you log your nights.