About 90-minute cycles

Sleep happens in ~90-minute cycles. Waking at the end of a cycle (rather than mid-cycle) generally feels more refreshing. We add ~14 minutes to fall asleep when you choose "now".

Frequently Asked Questions

Is the Sleep Cycle Calculator free to use?

Yes, the Sleep Cycle Calculator is 100% free to use. There are no subscriptions, no sign-ups, and no hidden fees.

Is my data safe when using the Sleep Cycle Calculator?

Absolutely. All calculations performed by the Sleep Cycle Calculator happen locally in your web browser. We do not store, track, or transmit your inputs or results to any server.

How accurate is the Sleep Cycle Calculator?

Our Sleep Cycle Calculator uses industry-standard formulas and methodology. You can view the exact formula and calculation logic used in the methodology section above to verify the math yourself.

Can I use the Sleep Cycle Calculator on my mobile phone?

Yes! The Sleep Cycle Calculator is fully responsive and works seamlessly on all devices including smartphones, tablets, and desktop computers.