Sleep Calculator
Find the perfect bedtime or wake-up time based on 90-minute sleep cycles.
09:46 PM
9h of sleep
6 cycles
Excellent — 9h sleep
11:16 PM
7h 30m of sleep
5 cycles
Great — 7.5h sleep
12:46 AM
6h of sleep
4 cycles
Good — 6h sleep
02:16 AM
4h 30m of sleep
3 cycles
Fair — 4.5h sleep
03:46 AM
3h of sleep
2 cycles
Poor — 3h sleep
05:16 AM
1h 30m of sleep
1 cycle
Poor — 3h sleep
How it works
Sleep happens in 90-minute cycles. Waking up at the end of a cycle (rather than in the middle) means you'll feel more refreshed. This calculator also adds 14 minutes for the average time to fall asleep.
- 100% free — no account needed
- Runs in your browser
- Nothing is uploaded
Frequently asked questions
Is Sleep Calculator really free?
Yes. Sleep Calculator is completely free on PureBrowser — every feature, with no account, no trial, and no credit card.
Does Sleep Calculator upload my data?
No. Sleep Calculator runs entirely inside your browser, so anything you type, paste, or open stays on your own device.
Do I need to sign up or install anything?
Neither. There is no account and nothing to download — open the page and Sleep Calculator is ready to use on desktop or mobile.
Does Sleep Calculator work offline?
Once the page has loaded, yes. All of the processing happens locally in your browser, so it keeps working without a connection.
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