Sleep Calculator
Estimate sleep duration and cycle times.
Estimated sleep duration
8 hr 15 min
- Time in bed
- 8 hr 30 min
- Approximate 90-minute cycles
- 5.5
What-if comparison
- 6 cycles from bedtime
- 7:45 AM
- 5 cycles from bedtime
- 6:15 AM
- 4 cycles from bedtime
- 4:45 AM
Sleep cycles vary between people and nights; these times are estimates, not medical advice.
What this calculator does
Compare bedtime and wake time across midnight, accounting for sleep latency and awake time.
Inputs and what they mean
- Bedtime
- — time value.
- Wake time
- — time value.
- Time to fall asleep
- — number value.
- Awake during the night
- — number value.
How to use it
- Enter the requested values.
- Adjust optional assumptions for your situation.
- Review the result and detailed breakdown.
Formula
Estimated sleep = wake time − bedtime (crossing midnight when needed) − sleep latency − awake time. Cycle scenarios use 90 minutes per cycle.
Worked example
10:30 PM to 7:00 AM
With 15 minutes to fall asleep, estimated sleep is 8 hours 15 minutes.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
Results depend entirely on the figures you enter and are rounded for display. They are for general information and education, not professional advice.
Common questions
Related tools
Calculate elapsed hours and minutes between two times, including overnight.