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Sleep Cycle and Optimal Bedtime Calculator

Best bedtime to wake refreshed based on 90-min cycles.

Calculates optimal bedtimes based on 90-minute sleep cycles. Waking at the end of a cycle (90, 180, 270, 360, 450, 540 min) minimises grogginess.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Bedtime = Wake_time − (n_cycles × 90 min + 15 min to fall asleep)

In depth

Calculates optimal bedtimes based on 90-minute sleep cycles. Waking at the end of a cycle (90, 180, 270, 360, 450, 540 min) minimises grogginess.