Sleep Debt Calculator

How it is calculated

The tool subtracts what you sleep from what you need and multiplies by the number of nights: nightly deficit = need − actual, debt = nightly deficit × days and equivalent nights = debt / need. All sleep values are in hours, so 6 h 30 min is 6.5. Need must be above 0 and at most 14 hours, actual sleep between 0 and 24, and the number of nights above 0 and at most 365; anything outside returns no result. It is a straight sum, with no weighting of recent nights, no interest on the debt and no credit for naps. If you sleep more than you need the figures turn negative, which means a surplus rather than a debt.

Common mistakes

• Typing 6.30 for six and a half hours: the field is decimal hours, so 6 h 30 min is 6.5, and 6.3 means about 6 h 18 min.
• Entering the time in bed instead of the time actually asleep; the debt then looks smaller than it is.
• Using a need number of 8 for everyone: your own need may be lower or higher, and the whole result scales with it.
• Treating the debt as something a single long weekend sleep-in repays exactly; the tool counts hours only and says nothing about recovery.
• Entering a long, uneven period as one average: seven nights of 4 h and seven of 8 h give the same debt as 6 h every night, which hides the bad nights.