Sleep Calculator: The Complete Guide
Wake up feeling refreshed. Choose when you want to wake up (or go to bed) and the sleep calculator suggests times based on 90-minute sleep cycles, so you rise between cycles rather than mid-sleep.
Who the Sleep Calculator is for
People who want to time sleep around natural cycles to wake up less groggy.
How to use the Sleep Calculator
- Type your values into the fields above — pick your currency or units where the calculator offers them.
- Results update automatically as you type; there's no submit button and nothing is sent to a server.
- Adjust any input to compare scenarios, then copy the result with a single click.
How it works
Sleep runs in roughly 90-minute cycles. Working back (or forward) from your chosen time — plus about 15 minutes to fall asleep — the calculator finds times that complete whole cycles (4–6 cycles ≈ 6–9 hours).
Features
- Bedtime or wake-time mode
- 90-minute cycle timing
- Several options
- Allows time to fall asleep
Why sleep cycles matter
Sleep moves through cycles of light, deep, and REM sleep lasting about 90 minutes. Waking at the end of a cycle — rather than in the middle of deep sleep — tends to leave you feeling more refreshed. By counting whole cycles from your target time and allowing time to fall asleep, this calculator suggests when to go to bed or set your alarm.