Mondo Knows Tools
Sleep Calculator
Best bedtimes, wake times, or how much sleep you owe yourself. Use the free sleep calculator below to get an instant answer, with the formula shown so you can check the maths and trust the result. Free, private, and no sign-up.
min
Mondo says
Recommended bedtime
23:15
6 cycles (9h): 21:45
5 cycles (7.5h): 23:15
4 cycles (6h): 00:45
3 cycles (4.5h): 02:15
How it works
Sleep runs in roughly 90 minute cycles. Waking between cycles feels far better than waking mid-cycle, so this counts back in 90 minute blocks from your target time.
Sleep Calculator: common questions
- What does the Sleep Calculator work out?
- Best bedtimes, wake times, or how much sleep you owe yourself. It is one of the Everyday & Tech tools on Mondo Knows.
- How is the Sleep Calculator calculated?
- Sleep runs in roughly 90 minute cycles. Waking between cycles feels far better than waking mid-cycle, so this counts back in 90 minute blocks from your target time.
- Do I need to sign up, and is my data stored?
- No sign-up, and nothing you type is sent anywhere. The calculation runs in your own browser, so the figures stay on your device and the page works offline once loaded.
Mondo also knows
Facts that connect to the sleep calculator
Short, sourced facts that point back to this tool.
The brain flushes metabolic waste products while you sleepCerebrospinal fluid sweeps through tissue spaces to remove toxic proteinsThe suprachiasmatic nucleus controls internal body clock rhythmsTiny cluster of hypothalamic cells uses light input to sync biological timingCore body temperature drops naturally during night sleepThermoregulatory cooling lowers metabolic rate to conserve resting energyEye muscles are the most active muscles in the human bodySix delicate muscles move each eye over one hundred thousand times daily
Estimates for general guidance only. This is not financial, medical or legal advice. Everything runs in your browser and nothing you type is stored.