Sleep Debt Calculator (Hours Owed and Days to Repay)
Adds up the shortfall between the sleep you need and the sleep you actually get, then shows how many nights a safe extra hour takes to clear the debt.
Recent
Formula
How the calculation works
The tool subtracts the hours you actually slept from the hours you needed and never lets the gap go below zero.
It multiplies that nightly gap by the number of nights to get the total hours of sleep debt.
It divides the debt by the safe extra hours a night and rounds up to give the number of days to repay.
Common mistakes
- Trying to repay a week of debt with one long weekend lie-in, which disrupts the body clock more than it helps.
- Counting a restless night as full sleep, when broken sleep repays far less of the debt than continuous sleep.
When to use it
- See how much sleep you owe after a run of late nights during exams or a heavy work week.
- Work out how many extra rest hours a night it takes to repay the debt without shocking your body.
Worked example
Needing 8 hours but sleeping 6 for 10 nights builds a debt of 20 hours, which clears in 20 days once you add 1 extra hour a night.
Common questions
How many extra hours a night are safe for repaying sleep debt?
One to two extra hours a night is a safe pace, and piling on more than that tends to disturb the next night's sleep.
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