Sleep Cycle Calculator

How It Works

The calculator uses a simple timing model: it adds your chosen fall-asleep delay, then counts forward or backward in 90-minute blocks. For a target wake-up time, it subtracts the delay and the selected number of cycles to suggest bedtimes. For a planned bedtime, it adds the delay and the selected number of cycles to suggest wake-up times.

Example

If you want to wake up at 7:00 AM and you usually need about 15 minutes to fall asleep, the tool works backward by 4, 5, and 6 cycles. That creates a shorter option around 12:45 AM and stronger target windows earlier in the night.

When to use this calculator

• Use it when you want to work backward from a wake-up time into a more deliberate bedtime.
• Use it when you are about to sleep now and want a few wake-up targets that match rough sleep cycles.
• Use it when your weekly routine feels inconsistent and you need a simple timing framework before changing harder habits.

Best ways to use the schedule

• Choose a realistic wake-up goal first, then work backward to find a bedtime window.
• Use the “current time” action when you want a quick answer for sleeping now.
• Keep the same wake-up rhythm for workdays and lighter days when possible so your body clock stays steadier.

What the estimate cannot tell you

• It does not measure sleep quality or sleep debt.
• It does not account for interruptions, shift work, or clinical sleep issues.
• It cannot replace medical guidance if you regularly struggle with sleep.

Practical planning tips

• Use the 5-6 cycle range as the main target window.
• Treat the 4-cycle option as a shorter backup instead of the ideal plan.
• If you usually need more or less time to fall asleep, adjust the delay field before trusting the result.