To calculate sleep efficiency, divide your total time asleep by your total time in bed, then multiply by 100. In bed for 8 hours and asleep for 7, your sleep efficiency is 7 / 8 x 100 = 87.5%. About 85% or higher is the usual benchmark for good sleep in adults.
The sleep efficiency calculator works it out from four numbers. Here's how to do the same math yourself, including the two pieces most people get stuck on: sleep latency and WASO.
Free toolSleep Efficiency CalculatorWhat share of your time in bed you actually spend asleep.What is the sleep efficiency formula?
Sleep efficiency is the percentage of your time in bed that you spend asleep.
Sleep efficiency (%) = total sleep time / time in bed x 100
And total sleep time comes from:
Total sleep time = time in bed - sleep latency - WASO - time awake before getting up
So you need four numbers: time in bed, how long it took to fall asleep (sleep latency), how long you were awake in the night (WASO), and how long you lay awake after your final wake-up.
How to calculate sleep latency
Sleep latency is the time from lights-out to falling asleep. Sleep latency = time you fell asleep - time you started trying to sleep.
If you turned off the light at 11:00 PM and think you dropped off around 11:40 PM, your sleep latency is 40 minutes.
Start the clock when you begin trying to sleep, not when you climb into bed with your phone. Researchers themselves have debated this point, and for a personal estimate, lights-out is the fairer starting line. Around 10 to 20 minutes is typical; more in how long it takes to fall asleep.
How to calculate WASO
WASO stands for wake after sleep onset: all the time you spend awake after first falling asleep, up to your final wake-up. WASO = the sum of every awake stretch during the night.
Say you woke three times:
- 1:30 AM, awake about 10 minutes
- 3:15 AM, bathroom and lying awake, about 25 minutes
- 5:00 AM, about 15 minutes
WASO = 10 + 25 + 15 = 50 minutes.
Very short wake-ups of a minute or two are normal, and you usually won't remember them. Count the ones you do remember and round up if unsure.
Worked example: how do you calculate sleep efficiency?
Here's a full night:
| Step | Value |
|---|---|
| Lights out | 10:30 PM |
| Out of bed | 6:30 AM |
| Time in bed | 8 h 0 min (480 min) |
| Sleep latency | 25 min |
| WASO | 35 min |
| Total sleep time | 480 - 25 - 35 = 420 min (7 h) |
| Sleep efficiency | 420 / 480 x 100 = 87.5% |
A second example with early waking: in bed 11:00 PM to 7:00 AM (480 minutes), 15 minutes to fall asleep, 20 minutes of WASO, and 15 minutes lying awake after waking for good. Total sleep is 430 minutes, so efficiency is 430 / 480 x 100 = 89.6%.
Some quick comparisons:
| Time in bed | Time asleep | Sleep efficiency |
|---|---|---|
| 7 h 0 min | 6 h 40 min | 95.2% |
| 7 h 30 min | 7 h 0 min | 93.3% |
| 8 h 0 min | 7 h 30 min | 93.8% |
| 8 h 0 min | 7 h 0 min | 87.5% |
| 8 h 0 min | 6 h 30 min | 81.3% |
| 9 h 0 min | 7 h 0 min | 77.8% |
For the bigger picture on why extra time in bed often buys more time awake, not more sleep, see time in bed vs time asleep.
What is a good sleep efficiency percentage?
For adults, 85% or higher is generally treated as good. A National Sleep Foundation expert panel on sleep quality agreed that sleep efficiency, sleep latency and WASO are all appropriate markers of good sleep quality, and set benchmarks for them:
| Measure | Sign of good sleep quality |
|---|---|
| Sleep efficiency | 85% or higher |
| Sleep latency | 30 minutes or less |
| WASO | Less is better; the panel treated shorter wake time as a marker of good quality |
On an 8-hour night, 85% efficiency means about 6 h 48 min asleep. The sleep efficiency calculator labels 85% and up as good, 75 to 84% as fair, and under 75% as low.
Efficiency close to 100%, where you fall asleep instantly and never stir, isn't always a good sign. It can mean you're short on sleep.
Sleep efficiency also shows up in research tools. The Pittsburgh Sleep Quality Index, a widely used sleep questionnaire, includes habitual sleep efficiency as one of its components.
Tips for a more accurate calculation
- Average a week, not one night. A single bad night can drag efficiency down 10 points.
- Estimate in the morning. Clock-watching at night tends to keep you awake.
- Keep the same rules each night, so your numbers are comparable.
- Don't chase 100%. Aim to stay above about 85% most nights.
If your efficiency stays low for weeks, the most effective fix is usually behavioral: go to bed only when sleepy and get up if you can't sleep. See is it bad to lie in bed awake. If poor sleep has lasted weeks or you're exhausted in the day, talk to a doctor.