Sleep Cycle Calculator
Best bedtimes based on 90-minute sleep cycles.
Amortization schedule
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Introduction
Sleep Cycle Calculator — Best bedtimes based on 90-minute sleep cycles. Enter Wake-up time to get an instant, accurate result.
Formula
Suggested bedtime = wake time − (N × 90 minutes) − 14 minutes to fall asleep, for N = 6 down to 2 sleep cycles.
Step-by-step
- Enter the Wake-up time.
- Click Calculate to see your result instantly.
Real-world example
Example: With Wake-up time = 07:00, the Sleep Cycle Calculator gives Bedtimes: 6, 21:46, 5, 23:16, 4, 00:46, 3, 02:16, 2, 03:46.
Frequently Asked Questions
Why 90-minute cycles?
A full sleep cycle (light sleep, deep sleep, REM) averages about 90 minutes, and waking between cycles rather than mid-cycle tends to feel less groggy.
Why subtract 14 minutes?
It's a commonly used estimate for the average time it takes to fall asleep after getting into bed.
What inputs does the Sleep Cycle Calculator need?
You'll need to provide: Wake-up time. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Sleep Cycle Calculator?
The Sleep Cycle Calculator applies the formula exactly as calculated — Suggested bedtime = wake time − (N × 90 minutes) − 14 minutes to fall asleep, for N = 6 down to 2 sleep cycles. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Sleep Cycle Calculator free to use?
Yes, the Sleep Cycle Calculator is completely free, requires no signup, and runs instantly in your browser.
About the Sleep Cycle Calculator
The Sleep Cycle Calculator uses a real, verifiable formula — Suggested bedtime = wake time − (N × 90 minutes) − 14 minutes to fall asleep, for N = 6 down to 2 sleep cycles. — so results are accurate every time, not an approximation.