Free OnlineCalculators & Converters
Sleep Calculator
Calculate the best time to go to bed or wake up based on 90-minute sleep cycles. Wake up refreshed by timing your sleep to complete full cycles.
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Assumes ~14 minutes to fall asleep + 90-minute sleep cycles.
Go to bed at…
3:46 AM
2 cycles · 3h sleep
2:16 AM
3 cycles · 4h 30m sleep
12:46 AM
4 cycles · 6h sleep
11:16 PM
5 cycles · 7h 30m sleep
9:46 PM
6 cycles · 9h sleep
Recommended Sleep by Age
School-age children (6–12)9–12 hours
Teenagers (13–18)8–10 hours
Adults (18–64)7–9 hours
Older adults (65+)7–8 hours
Key Features — Sleep Calculator
Wake-up time to ideal bedtimes
Bedtime to ideal wake-up times
2–6 sleep cycle options
Accounts for 14-min sleep onset time
Recommended cycles highlighted
Sleep by age guidelines
Why Use This Tool — Sleep Calculator
Free Online Sleep calculatorSleep cycle calculator — for EveryoneFast & Easy When to wake upBest time to sleep — 100% FreeFree Online Bedtime calculator
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Works Everywhere
Use on any device — desktop, tablet, or phone. No downloads or plugins needed.
Frequently Asked Questions — Sleep Calculator
What is a sleep cycle?
A sleep cycle is approximately 90 minutes of sleep progressing through light sleep, deep sleep, and REM sleep stages. Most adults complete 4–6 cycles per night. Waking up between cycles — rather than during deep sleep — helps you feel more refreshed.
Why 14 minutes to fall asleep?
The average adult takes about 10–20 minutes to fall asleep (sleep latency). The calculator uses 14 minutes as the default, meaning your alarm should be set 14 minutes after your actual target sleep time. If you fall asleep faster or slower, adjust your bedtime accordingly.
How many sleep cycles should I get?
Most adults need 5–6 complete sleep cycles (7.5–9 hours) per night. Getting fewer than 4 cycles (6 hours) is associated with impaired cognition and health risks. The calculator highlights 5–6 cycles as recommended for adults.