Sleep Calculator
Calculate the best bedtimes or wake times based on 90-minute sleep cycles.
Aim for 5–6 sleep cycles (7.5–9 hours) for the best rest.
How Sleep Cycles Work
A complete sleep cycle is about 90 minutes long and includes light sleep, deep sleep, and REM. Waking up at the end of a cycle (rather than mid-deep sleep) leaves you feeling refreshed instead of groggy. Most adults need 5–6 cycles per night, plus about 14 minutes to actually fall asleep.
How to Use the Calculator
If you know what time you need to wake up, choose the wake mode and enter your alarm time — the tool will show you ideal bedtimes. If you're heading to bed now, choose bed mode and enter your current time to see when you should set your alarm.
FAQ
Why 90 minutes?
That's the average length of one full sleep cycle for adults. It varies slightly per person but 90 minutes is a reliable approximation.
How many cycles do I need?
Most adults feel best with 5 or 6 cycles (7.5 to 9 hours). 4 cycles (6 hours) is a minimum for short nights.
Why add 14 minutes?
The average healthy adult takes about 14 minutes to fall asleep after lying down. The calculator factors this in.
Does this work for naps?
For a quick boost, take a 20-minute nap. For full restoration, take a 90-minute nap (one full cycle).
Is anything saved?
No. The tool runs entirely in your browser.
Love using BreezyTools?
Go Pro for an ad-free experience, priority features, and support independent development — for less than a coffee a month.