Sleep debt calculator
Seven nights, your target, and the shortfall that's left over.
Your last seven nights
- Average night
- hours
- Shortest night
- hours
- Nights below target
- of
- Running shortfall
- hours
Nothing to repay over this stretch — you slept hours more than your own target across the week.
At the extra hours you entered, that shortfall divides into more nights.
That last figure is division, not physiology. Recovery isn't linear, and lost sleep isn't repaid hour for hour — so read it as "at this rate", not as a prediction about how you'll feel.
Those numbers don't add up — check that every night is between 0 and 24 hours and that your target is a real number of hours.
How it works out the number
It multiplies your target by the number of nights, subtracts what you actually slept, and shows the difference. Nights where you slept more than your target count in your favour, so a long weekend genuinely offsets a short week in the arithmetic.
"Nights to clear" is that shortfall divided by the extra hours you say you could add. It's division, and nothing more. Sleep recovery isn't linear, and there is no good evidence that lost sleep is repaid hour for hour — so the figure tells you how big the hole is in units of nights, not when you'll feel better.
A week is the right window
Seven nights is long enough to include a weekend and short enough that you can still remember it. If you're guessing wildly at every number, the output is a guess too — a fortnight of writing down when you actually fell asleep beats a month of estimates.
If the number keeps coming back large
A persistent shortfall is either a schedule problem or a sleep problem, and they need different answers. If you're in bed for long enough and still short — or still exhausted — that's the case for thesymptom questionnaire, and then a doctor. If it's a schedule problem, theshift planner is the more useful tool.
Not sure what your target should be?Check the range for your age.