Bedtime Calculator
Enter the time you need to wake up and calculate several possible bedtimes using an adjustable sleep-cycle estimate and fall-asleep buffer.
What time should you go to bed?
Start with your required wake time, then count backward by your estimated fall-asleep time and several possible cycle counts. The calculator uses 90 minutes as an adjustable default rather than claiming every sleep cycle is exactly the same length.
Wake time minus estimated sleep
For each result, the calculator subtracts your fall-asleep buffer and then subtracts the selected cycle length multiplied by 3, 4, 5 or 6 cycles. Because actual sleep cycles vary, treat the outputs as planning windows rather than exact biological targets.
Sleep timing is an estimate. A clock-based calculator cannot measure your actual sleep stage or sleep quality.
How to use this calculator
- 1
Enter the clock time you need to wake up.
- 2
Adjust the estimated cycle length or fall-asleep buffer if desired.
- 3
Compare the possible bedtimes and total estimated sleep shown in the results.
Bedtime Calculator FAQ
Does the bedtime calculator assume every cycle is 90 minutes?
No. Ninety minutes is the default planning value, and you can adjust the estimate from 80 to 100 minutes.
Why are several bedtimes shown?
The tool compares multiple possible cycle counts instead of presenting one calculated time as universally correct.
Should I choose a shorter bedtime just because it ends on a cycle boundary?
No. Total sleep duration remains important. Cycle calculations should not be used to justify routinely reducing sleep.