Sleep Calculator
Calculate the best time to go to bed or wake up online free using 90-minute sleep cycles. Free online sleep calculator and bedtime planner for all ages.
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Part of the toolkit
How to use Sleep Calculator
- 1Choose whether you know your wake-up time, your bedtime, or are going to sleep right now
- 2Enter the time, how long you usually take to fall asleep and your age group
- 3Pick one of the suggested bedtimes or alarm times — each ends a full 90-minute sleep cycle; highlighted options give enough sleep for your age
Frequently asked questions
How does the sleep calculator work?▾
Sleep runs in cycles of about 90 minutes. Waking at the end of a cycle, in light sleep, usually feels easier than waking in deep sleep. The calculator counts back (or forward) whole cycles from your time and adds the minutes you need to fall asleep.
What time should I go to bed to wake up at 7 AM?▾
With 15 minutes to fall asleep: 9:45 PM for 6 cycles (9 h), 11:15 PM for 5 cycles (7.5 h), or 12:45 AM for 4 cycles (6 h). Most adults should aim for 5–6 cycles.
How much sleep do I need?▾
The National Sleep Foundation recommends 7–9 hours for adults, 8–10 for teens, 9–11 for school-age children and 7–8 for adults over 65.
Is every sleep cycle exactly 90 minutes?▾
No — cycles range from about 80 to 120 minutes and vary through the night, so treat the times as a helpful guide and adjust by 10–15 minutes if you still wake up groggy.
Embed Sleep Calculator on your website▾
Paste this snippet into your page. The embedded tool runs in your visitor's browser and shows a small “Powered by clkr.work” link.