How to Use Sleep Calculator
Wake up refreshed by timing your sleep in complete 90-minute cycles. Enter your wake-up time to see ideal bedtimes, or your bedtime to see ideal alarm times.
Open the Sleep Calculator tool →What is Sleep Calculator?
Find the best bedtimes or wake-up times based on 90-minute sleep cycles. It's completely free, needs no sign-up, and runs entirely in your browser — so it's fast and private.
How to use Sleep Calculator
- Open the Sleep Calculator tool.
- Enter your details or values.
- The result is calculated instantly.
- Copy or use the result. Everything runs in your browser — nothing is uploaded.
Frequently asked questions
How does it pick bedtimes?
It works around 90-minute sleep cycles, so you wake at the end of a cycle rather than mid-cycle when you feel groggy.
Why 90 minutes?
A full sleep cycle averages about 90 minutes, and waking between cycles tends to feel more refreshing.
Is this a guarantee?
No — cycle length varies by person and night, so treat the times as helpful targets.
Ready to try it?
Open Sleep Calculator →