Sleep Cycle Calculator
90-minute sleep cycles drive when you wake up feeling alert. Find the wake-up times that land between cycles.
Scan to open on your phone
Point your phone camera at the code to open this tool.
90-minute sleep cycles drive when you wake up feeling alert. Find the wake-up times that land between cycles.
How to use Sleep Cycle Calculator
- Open the toolNo signup and nothing to install; it works as soon as the page loads.
- Set “Bedtime (24h, e.g. 23:00)”
- Read the resultChange any input and the result is recalculated immediately.
Worked example with the defaults
- SUGGESTED WAKE TIMES · Based on 90-minute sleep cycles
- 05:00 · 06:30 · 08:00
Nothing you enter leaves your device
All of the work happens inside your browser. Whatever you type is never packaged up and sent to a server, and no request this page makes carries it.
That makes it safe for contract amounts, personal details and internal documents you would rather not hand to a third party — close the tab and it is gone.
What this tool does not do
Sleep Cycle Calculator only does what a browser can do on its own — it talks to no backend service. So it keeps no history for you and syncs nothing across devices; if you need a record, copy or download the result.
It is also not a substitute for professional judgement. For legal, medical or tax decisions, treat the output as a starting point rather than a final answer.
Frequently Asked Questions
- What is a sleep cycle?
- One cycle runs through light sleep, deep sleep and REM, lasting roughly 90 minutes. Waking near the end of a cycle usually feels easier than waking in deep sleep.