Sleep Calculator
Suggest bedtimes or wake times aligned to ~90 minute sleep cycles. Fully client-side — no account, uploads, or remote storage.
Added Apr 18, 2026 · Updated Apr 21, 2026
Input
Result
Enter a value for i want to know… to see your result.
How it works
Calculates optimal sleep or wake times based on 90-minute sleep cycles. Each full cycle includes light sleep, deep sleep, and REM sleep. Waking between cycles (rather than during them) typically feels more refreshing.
Step by step
- 01Choose whether you want wake-up times (given your bedtime) or bedtimes (given your wake-up time).
- 02Enter the relevant time and how long you typically take to fall asleep.
- 03The tool calculates times aligned with 4, 5, and 6 complete 90-minute sleep cycles.
- 04Aim for 5–6 cycles (7.5–9 hours) for most adults.
Examples
Bedtime 23:00, when to wake
23:00 + 14 min + 6×90 min = 08:14 AM for 6 full cycles (next day), shown with 12-hour times in the table.
Inputs
- I want to know…:
- wake
- Bedtime:
- 23:00
- Minutes to fall asleep:
- 14
Result
- Recommended times:
- {"headers":["Wake-up time","Cycles","Duration","Quality"],"rows":[["08:14 AM","6","9 hrs","★★★ Best"],["06:44 AM","5","7.5 hrs","★★ Good"],["05:14 AM","4","6 hrs","★ Minimum"]]}
- Note:
- Based on 14-min fall-asleep time + 90-min sleep cycles.
Frequently asked questions
Why 90-minute cycles?
A typical sleep cycle lasts ~90 minutes and includes light sleep, deep sleep (slow-wave), and REM (rapid eye movement) sleep. Waking at the end of a cycle, when you're in light sleep, tends to feel more natural and less groggy than being woken during deep sleep.
How many sleep cycles do I need?
Most adults need 5–6 cycles per night (7.5–9 hours). Teenagers may need 6–8 cycles. Athletes and people recovering from illness often benefit from extra sleep.