Free · Everyday · Date & Time

Sleep Calculator

Plan bedtimes or wake times around approximate 90-minute sleep cycles and a settling allowance.

  • Checked formula
  • Private in your browser
  • No signup
Calculator inputs

Enter your values

Result

Your calculation

Suggested bedtimes
21:45 (6 cycles); 23:15 (5 cycles); 00:45 (4 cycles)
Cycle assumption
90 minutes
Settling allowance
15 minutes

Sleep cycles vary substantially. Consistent sufficient sleep matters more than hitting an exact cycle boundary.

How to use this calculator

  1. Enter the values and choose the units that match your situation.
  2. Calculate to see the primary answer and useful conversions.
  3. Review the assumptions before using the result for a project or decision.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.