😴 Sleep Calculator

What is Sleep Calculator?

The Sleep Calculator turns one anchor time into a full sleep schedule built on 90-minute sleep cycles. Choose a wake-up time and it works backward to suggest the best bedtimes, or choose a bedtime and it works forward to the best times to wake, so you always finish a whole number of cycles. Each option shows how many cycles it gives you and its total sleep duration, with your chosen target cycle count highlighted as recommended. Everything is calculated in your browser with no account and no data upload.

How to Use Sleep Calculator

1. Choose whether you are planning from a wake time or a bedtime
2. Enter the anchor time and pick your target number of cycles
3. Read the recommended schedule and the full list of cycle options

Why Use Our Sleep Calculator?

• Recommended bedtimes from your wake time, or wake times from your bedtime
• Schedules built on 90-minute sleep cycles with clear total durations
• A target-cycle selector from 4 to 6 with the best option highlighted
• Private, instant planning with nothing stored or uploaded

Common Use Cases

• Setting a bedtime the night before an early start
• Choosing the best time to go to sleep now for a fixed wake-up
• Checking how much sleep a given bedtime or wake time actually allows

Frequently Asked Questions

• How many sleep cycles do I need?▾
  Most adults feel best after 5 to 6 full 90-minute cycles, which is about 7.5 to 9 hours of sleep. The calculator lets you aim for 4, 5 or 6 cycles and shows the matching bedtimes or wake times.
• Is 7 to 9 hours of sleep enough?▾
  Seven to nine hours is the usual recommendation for adults, which equals roughly five to six 90-minute cycles. Children and teenagers usually need more sleep, so they should aim toward the higher end or add an extra cycle.
• Why is it better to wake at the end of a sleep cycle?▾
  Sleep alternates between light, deep and REM stages in cycles of about 90 minutes. Waking during deep sleep leaves you groggy, while waking at the end of a cycle, when sleep is lightest, makes you feel more refreshed.