Sleep debt calculator
Sleep debt is the gap between the sleep you needed and the sleep you got. Enter your nightly need and the hours you slept over the last seven nights to see how far behind or ahead the week is.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Enter how many hours you need per night. Decimals work: 7.5 is seven and a half hours.
- Enter the hours you actually slept on each of the last seven nights.
- Read the weekly debt, the average night and the extra minutes per night that would clear it in a week.
How it is calculated
- Total needed = nightly need × 7.
- Total slept = the sum of the seven nights.
- Debt = total needed − total slept. If you slept more than you needed, the debt is 0 and the balance reads as a surplus.
- Extra per night = debt ÷ 7, shown in minutes.
Worked example
Need 8 h. Slept 6.5, 6, 7, 6, 6.5, 8.5 and 9 hours: total 49.5 h against 56 h needed. The debt is 6.5 h, and the average night was 7.07 h. Spread over seven nights, that is about 56 extra minutes per night.
Tips
Use sleep time, not time in bed, and be honest about the nights. Healthy habits such as a regular wake-up time and a dark, cool room help, but this tool only does the counting and gives no diagnosis.
Frequently asked questions
What is sleep debt?
Sleep debt is the cumulative difference between the sleep your body needs and the sleep you actually get. Seven nights of 6 hours when you need 8 adds up to 14 hours of debt.
How many hours of sleep do I need?
The AASM and Sleep Research Society consensus statement (Watson et al., 2015) recommends that adults sleep 7 or more hours per night. Individual needs differ, so use the number that leaves you rested and alert.
Can I catch up on sleep at the weekend?
Some extra sleep helps, but a rule of thumb is that it is easier and gentler to add a little each night than to repay a large debt in one go. The extra-per-night figure here simply divides the debt over seven nights.
Does a long night cancel a short one?
In this calculator, yes, arithmetically: the balance is total slept minus total needed over the week. Whether a long sleep fully undoes the effects of short ones is not something a calculator can say.
Is this a medical assessment?
No. It is simple arithmetic on the numbers you enter. If you are always tired despite enough sleep, or you snore loudly or stop breathing at night, ask a doctor.