Sleep Estimator Calculator
Estimate how much sleep you will really get. Enter your bedtime, wake up time, how long you take to fall asleep and how long you are awake in the night, then see the result against the usual range for your age.
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Free sleep estimator calculator
A sleep estimator takes your bedtime and wake up time, removes the time you spend falling asleep and lying awake, and gives you the sleep you are likely to get, along with full cycles and how that compares with the usual range for your age.
Fill in your plan for tonight, or choose to go to bed now. The estimate is only as good as the guesses you enter, so be honest about how long you take to fall asleep.
How the sleep estimate is calculated
- Time in bed = wake up time minus bedtime, counted across midnight when needed.
- Estimated sleep = time in bed minus time to fall asleep minus time awake in the night.
- Full cycles = estimated sleep divided by 90 minutes, rounded down, with the leftover minutes shown.
- Sleep efficiency = estimated sleep divided by time in bed, as a percentage.
The range you are compared against comes from published guidance. For adults it is the American Academy of Sleep Medicine and Sleep Research Society recommendation of 7 or more hours. For children and teenagers it follows the age bands used by the CDC. Ages 1 to 5 include naps, and this tool counts only the night you enter, so treat that result as a guide.
Reading your result
Three results matter most.
- Estimated sleep is the number to compare with your age range. Below the range means you are short, and the page shows how much earlier to go to bed.
- Sleep efficiency shows how much of your time in bed is spent asleep. A low figure with a long time in bed often points to lying awake, which is a different problem from not allowing enough time.
- Full cycles is a planning aid. Waking at the end of a cycle may feel easier for some people, but it is not a promise.
Example estimates
These rows are worked out the same way as the calculator, for an adult, so you can check how inputs change the result.
| Bedtime | Wake up | Fall asleep / awake | Time in bed | Estimated sleep | Full cycles | Efficiency |
|---|---|---|---|---|---|---|
| 11:00 PM | 6:30 AM | 15 / 0 min | 7 hours 30 minutes | 7 hours 15 minutes | 4 (+75 min) | 97% |
| 12:30 AM | 7:00 AM | 20 / 30 min | 6 hours 30 minutes | 5 hours 40 minutes | 3 (+70 min) | 87% |
| 10:00 PM | 6:00 AM | 10 / 15 min | 8 hours | 7 hours 35 minutes | 5 (+5 min) | 95% |
| 1:00 AM | 6:30 AM | 30 / 30 min | 5 hours 30 minutes | 4 hours 30 minutes | 3 (+0 min) | 82% |
The second row shows why time in bed can mislead: a 6.5 hour night in bed becomes a little over 5 and a half hours of real sleep once falling asleep and night waking are removed.
Sleep needs by age
| Group | Recommended sleep per day |
|---|---|
| Teenagers, 13 to 18 | 8 to 10 hours |
| Children, 6 to 12 | 9 to 12 hours |
| Children, 3 to 5 (with naps) | 10 to 13 hours |
| Children, 1 to 2 (with naps) | 11 to 14 hours |
| Adults, 18 to 60 | 7 or more hours |
| Adults, 61 to 64 | 7 to 9 hours |
| Adults, 65 and older | 7 to 8 hours |
For a deeper look at these ranges and what changes them, read how many hours of sleep you need. Children under 1 year have separate guidance, covered by the baby sleep calculator.
Sleep estimator or sleep calculator
They answer different questions. Use a sleep calculator or the sleep cycle calculator when you want suggested times to go to bed or wake up. Use the sleep estimator when you already have a plan, or you just went to bed, and want to know what sleep it will give you. The bedtime calculator is the quickest route from an alarm time to a bedtime.
Limits of a sleep estimate
People often misjudge how long they take to fall asleep and how often they wake, so the result is an estimate built on your own guesses. Wearables are estimates too. The reference measurement is a clinical sleep study. This tool does not diagnose anything. If you regularly sleep far less than you need, struggle to fall asleep, or feel very sleepy in the day, speak to a doctor.
Frequently asked questions
What is a sleep estimator?
A sleep estimator works out how much sleep you are likely to get from your bedtime and wake up time, after removing the time you spend falling asleep and lying awake, and compares the result with the usual range for your age.
How is estimated sleep different from time in bed?
Time in bed is the gap between lying down and getting up. Estimated sleep removes the minutes you take to fall asleep and the minutes you are awake in the night, so it is always shorter.
What is a good sleep efficiency?
Many sleep clinicians treat about 85 percent or higher as good. Your figure here depends on your own estimates of falling asleep and night waking, so use it as a rough guide.
How accurate is a sleep estimator?
It is only as accurate as the numbers you enter. People often misjudge how long they take to fall asleep, and wearables are estimates too. A clinical sleep study is the reference measurement.
How much sleep do I need?
Adults need 7 or more hours according to the American Academy of Sleep Medicine and Sleep Research Society. Teenagers are advised 8 to 10 hours and children aged 6 to 12 are advised 9 to 12 hours.
Can I use it for tonight?
Yes. Choose that you are going to bed now, enter the time you need to get up, and the tool uses your device clock as the bedtime.
How is this different from the sleep calculator?
The sleep calculator suggests times to sleep or wake. The estimator checks a plan you already have and tells you how much sleep it is likely to give you.