Sleep Calculator
Bedtimes and wake times aligned to 90-minute sleep cycles.
Best bedtimes
11:15 PM
for 5 sleep cycles (7.5 h)
6 cycles (9 h sleep)
9:45 PM
5 cycles (7.5 h sleep)
11:15 PM
4 cycles (6 h sleep)
12:45 AM
3 cycles (4.5 h sleep)
2:15 AM
ShowHide the working
- 1Each sleep cycle is about 90 minutes; waking between cycles feels more refreshing.
- 2Allowing 15 min to fall asleep.
Formula
90-minute sleep cyclesHow it works
Bedtimes or wake times that land at the end of a 90-minute sleep cycle, when waking feels easiest. Five to six cycles is a full night.
Example
To wake at 7:00 AM, going to bed around 9:45 PM gives six full cycles.
About the Sleep Calculator
Bedtimes and wake times aligned to 90-minute sleep cycles. It sits in the Date & Time section of NWS Calc, a free collection of calculators that run entirely in your browser. There is no signup, no paywall and no tracking — open the page, enter your numbers, get an answer.
Frequently asked questions
- Is the Sleep Calculator free to use?
- Yes. Every calculator on NWS Calc is completely free, with no signup, no usage limits and no ads.
- Does my data leave my device?
- No. The Sleep Calculator runs entirely in your browser using JavaScript. Nothing you type is uploaded, logged or stored on a server.
- Can I use the Sleep Calculator on my phone?
- Yes. The page is fully responsive and works in any modern mobile or desktop browser — there is nothing to install.
- What else is in Date & Time?
- Ages, durations, business days, countdowns and time zones. You can browse the full Date & Time category for related calculators.