Waking in the middle of a deep cycle is what makes eight hours feel like four. Tell us when you have to be up and we will work backwards to the times worth aiming for.
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Set your wake up time and we will list the bedtimes worth aiming for.
Sleep runs in cycles that last roughly 90 minutes each, moving from light sleep down into deep sleep and back up again. Waking at the top of a cycle feels easy. Being pulled out of the bottom of one is what leaves you groggy for an hour, and it is why a badly timed eight hours can feel worse than a well timed six.
This counts back from your wake up time in 90 minute blocks, and adds the time you take to fall asleep on top. Five or six cycles - seven and a half to nine hours - is where most adults should land.
No, and any tool claiming otherwise is overselling it. Cycles run anywhere from about 70 to 110 minutes, and yours change through the night. Treat these times as a target to aim near rather than a train to catch. The bigger win is going to bed at the same time every night, which makes your own cycles more predictable than any calculator can.
More than most people expect. Muscle is repaired during sleep, not during the session. Short sleep also makes hunger harder to manage the next day, which is the part that quietly undoes a calorie deficit. If you are training properly and eating properly and still going nowhere, sleep is the third thing to look at.
Most adults need seven to nine hours. Teenagers need more. The honest test is whether you wake without an alarm feeling rested - if you cannot, you are probably short, whatever the number says.
Sleep cycles vary between people and across the night, so these times are a target rather than a schedule. Everything on this page is worked out from a formula or from published averages. It has never met you, and it cannot see your blood pressure, your medication or an old injury.
Talk to a doctor before you start if you are pregnant or breastfeeding, have a heart condition, diabetes or high blood pressure, take regular medication, have or have had an eating disorder, are recovering from injury or surgery, or are under 18. Stop and get advice if any exercise causes pain, dizziness or chest discomfort.
More about where these numbers come from is on the about page.
