How this calculator works
The weekly result is an accounting comparison with your chosen target. Positive balance means fewer hours than planned; negative balance means more. Extra sleep is included in the arithmetic, but does not prove recovery from sleep loss. The overnight mode subtracts entered awake time from a local wall-clock interval; it ignores daylight saving and timezone changes, so adjust those intervals yourself. The result is an estimate for information only and is not medical advice.
Formula
Weekly balance = 7 × daily target - sum of the seven daily sleep durations. Average = total / 7. Target = (weekly balance + total) / 7. A missing day = 7 × target - weekly balance - the six known days; average = target - balance/7. Overnight sleep estimate = wake time - bedtime - time awake.
Worked example
Seven 7-hour days total 49 hours. Against 8 hours per day, the planned total is 56 hours and the shortfall is 7 hours. Seven 9-hour days instead give a signed balance of -7 hours.
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Frequently asked questions
Is sleep debt an exact biological quantity?
No. This is a simple hours-based estimate, not a model of alertness or recovery.
Can naps be included?
Yes. Include naps in each day total if the target represents all sleep in 24 hours.
What happens when clocks change?
Datetime entries are local wall-clock values. A clock change is not detected, so this mode cannot establish real elapsed time across it.