Sleep Calculator
Plan your night around complete 90-minute sleep cycles. Pick a wake-up time to see when to go to bed, or pick a bedtime to see when to wake up.
Last updated: June 20, 2026 · Medically reviewed by TG we-Calculate Editorial TeamI want to
Wake-up time
Head to bed by 9:46 PM for 9 hours of sleep
How does a sleep cycle calculator work?
A sleep cycle calculator counts back from your wake-up time (or forward from your bedtime) in 90-minute cycles, plus about 14 minutes to fall asleep. Waking at the end of a cycle, rather than mid-cycle, leaves you feeling more refreshed. Aim for 5–6 full cycles, roughly 7.5–9 hours.
Formula
How this is calculated
The calculator treats sleep as a repeating series of cycles, each averaging 90 minutes, that move through light sleep, deep sleep and REM. Waking at the boundary between cycles tends to feel less groggy than being roused mid-cycle, so the tool lines up your schedule with whole-cycle counts. The two inputs are a mode (whether you are fixing a wake-up time or a bedtime) and a single anchor time entered as HH:MM in 24-hour form.
From that anchor it applies one constant, a 14-minute sleep-onset latency, which is a typical average of the 10-20 minutes most people take to actually fall asleep, so the cycle count starts from when you are truly asleep. In wake mode it subtracts the latency plus N x 90 minutes from your wake time to find each candidate bedtime; in bed mode it adds the same amount to your bedtime. It does this for N = 6, 5, 4 and 3 cycles, giving 9, 7.5, 6 and 4.5 hours of sleep, and wraps any result across midnight into a 24-hour clock.
The 90-minute cycle and 14-minute latency are population averages, not personal measurements: real cycles vary by age, individual and night, and the tool ignores naps, awakenings and sleep debt. Times are computed on a fixed reference date and shown in your locale format, so output is purely arithmetic and never reads the real clock.
Examples
| Input | Result |
|---|---|
| Wake up at 07:00 | Best bedtimes: 21:46, 23:16, 00:46 or 02:16 |
| Go to bed at 23:00 | Best wake-up times: 06:44, 08:14 (after 5–6 cycles) |
| Go to bed at 22:30 | Wake at 07:44 for 6 full cycles (9 hours) |
Frequently asked questions
A full sleep cycle moves through light sleep, deep sleep and REM and lasts about 90 minutes on average. Waking at the end of a cycle, instead of in the middle of deep sleep, tends to feel less groggy.
Most people take 10 to 20 minutes to actually fall asleep after getting into bed. We use 14 minutes as a typical average so the cycle count starts from when you are truly asleep.
Most adults do best with 5 to 6 complete cycles per night, which is roughly 7.5 to 9 hours of sleep. Fewer than 4 cycles is generally not enough for ongoing health.
Also known as
Sources & references
TG we-Calculate Editorial Team. (2026). Sleep Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/sleep-calculator
TG we-Calculate Editorial Team. "Sleep Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/sleep-calculator.
TG we-Calculate Editorial Team, "Sleep Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/sleep-calculator
@misc{wecalculate_sleep_calculator, title = {Sleep Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/sleep-calculator}}, year = {2026}, note = {TG we-Calculate} }
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