Free tool
Sleep calculator
What time should you go to bed? Enter the time your alarm goes off and we’ll count backwards in 90-minute sleep cycles, so you wake at the end of one instead of being hauled out of the middle. Works the other way too, if you already know when your head hits the pillow. No email required — the calculators run entirely in your browser and store nothing. (There’s an optional newsletter box further down; the tools never ask.)
To wake at 7:00 am, go to bed at one of these times:
9:45 pm
6 cycles · 9 hrs
Recommended
11:15 pm
5 cycles · 7.5 hrs
Recommended
12:45 am
4 cycles · 6 hrs
2:15 am
3 cycles · 4.5 hrs
Sleep cycles average about 90 minutes, but they genuinely vary between people and lengthen across the night, so treat these as targets rather than a stopwatch. Waking at the end of a cycle tends to feel easier than being pulled out of the middle of one. If you take much longer than 30 minutes to fall asleep most nights, the buffer above is the number worth fixing first.
Sleep efficiency
How much of your time in bed is actually sleep?
Eight hours in bed is not eight hours of sleep. Sleep efficiency is the share of your time in bed that you spend asleep, and it is the single most useful number in sleep medicine because the fix it points to is often counterintuitive: spend less time in bed, not more.
7 hr 25 min asleep out of 8 hr in bed.
This is the range most people are aiming for. The time you spend in bed is mostly time asleep.
Sleep efficiency is simply time asleep divided by time in bed. It’s the number clinicians use in CBT-I, the first-line treatment for chronic insomnia, and it’s more useful than a proprietary sleep score because you can check the arithmetic yourself. Estimate the minutes rather than clock-watching — checking the time during the night makes sleep worse, and a rough figure is fine here. This is an educational calculation, not a diagnosis. If your efficiency sits low for weeks, that’s worth raising with a doctor, who may point you toward CBT-I rather than anything you can buy.
Step three
Right bedtime, still awake?
Then the clock isn’t the problem. Eight questions, two minutes: we score the six habits with the best-documented effects on sleep (duration, consistency, caffeine, alcohol, screens, and how fast you fall asleep) into a single percentage, then show you exactly where it’s leaking.
How much sleep do you actually get on a typical night?
Common questions
What time should I go to bed if I wake up at 6am?
Counting back in 90-minute sleep cycles and allowing about 15 minutes to fall asleep, a 6am alarm points to roughly 8:45pm (6 cycles, 9 hours) or 10:15pm (5 cycles, 7.5 hours). Most adults do best in that 7.5-to-9-hour band.
How long is a sleep cycle?
About 90 minutes on average, cycling through light sleep, deep sleep, and REM. Real cycles range from roughly 70 to 120 minutes and tend to lengthen through the night, so a calculator gives you a target, not a guarantee.
Is it better to wake up between sleep cycles?
Most people find it easier. Being woken out of deep sleep produces the groggy, heavy feeling known as sleep inertia, while waking near the end of a cycle, in lighter sleep, tends to feel cleaner even when total sleep is the same.
How many hours of sleep do I actually need?
Adult guidance is 7 to 9 hours a night, which is 5 to 6 full cycles. Consistently getting 6 hours or less is where the effects on mood, focus, and health start showing up in the research.
What is sleep efficiency, and what is a good score?
Sleep efficiency is the time you spend asleep divided by the time you spend in bed, expressed as a percentage. Above about 85% is the usual target. It is the metric clinicians work from in CBT-I, and when it is low the effective fix is often to spend less time in bed rather than more, so that bed stops being a place you lie awake.
For site owners
Put this calculator on your site
Free to embed on any site, personal or commercial, with no permission needed and no tracking pixels inside the frame. The only condition is that you keep the attribution line, which is the paragraph under the iframe. Paste this where you want it:
<iframe src="https://www.getnocte.com/tools/sleep-calculator/embed"
title="Sleep calculator by Nocte"
width="100%" height="820" loading="lazy"
style="border:0;max-width:640px"></iframe>
<p><a href="https://www.getnocte.com/tools/sleep-calculator">Sleep calculator</a> by <a href="https://www.getnocte.com">Nocte</a></p>
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</script>The small script at the end just resizes the frame to fit its contents, since the calculator is taller on a narrow column than a wide one. If your CMS strips inline scripts, delete that block and keep the rest: the embed still works, it will simply scroll inside its own frame on narrow screens.
Teachers, clinicians, and student-wellbeing sites: you are welcome to use it, and we’re happy to add a plain-language explainer or a different default wake time if that makes it more useful. Email hello@getnocte.com.