See how much sleep you’ve missed. This free sleep debt calculator compares your nightly target with actual hours slept over the week, showing total debt, average sleep and shortfall.
Set your nightly target, then enter how many hours you actually slept on each of the last seven nights. Leave a night blank if you’d rather not include it.
Sleep debt is the gap between the sleep you need and the sleep you get, added up over time. You can’t fully “bank” or repay it in one night, but a few nights of consistent, slightly longer sleep and a steady schedule help you recover.
How the Sleep Debt Calculator Works
This tool tallies the gap between how much sleep you’re aiming for and how much you actually got over the last week. Rather than just showing one night, it adds up the shortfall (or surplus) across every night you enter to give a total sleep debt figure.
Formula: Sleep debt = (Target hours × Nights counted) − Total hours slept. Average per night = Total hours slept ÷ Nights counted. Average shortfall per night = Target hours − Average per night. Only nights where you actually entered a value are counted; blank nights are skipped entirely.
- Target — the sleep you aim for per night, in hours.
- Nightly hours slept — up to 7 nightly entries for the last week; any night left blank is excluded from the total and the average.
Example Scenarios
| Target / Night | Nights Logged | Total Hours Slept | Sleep Debt |
|---|---|---|---|
| 8 h | 7 | 49 h | 7 h |
| 7 h | 7 | 49 h | 0 h |
| 8 h | 7 | 42 h | 14 h |
| 8 h | 3 | 24 h | 0 h |
| 7.5 h | 7 | 63 h | -10.5 h (surplus) |
| 8 h | 7 | 50 h | 6 h |
Sleep Debt Calculator FAQ
Can you actually “catch up” on sleep debt over a weekend?
A single long lie-in can ease tiredness somewhat, but it doesn’t fully repay a build-up of lost sleep the way this calculator’s running total might suggest. A few consecutive nights of consistent, slightly longer sleep tends to help more than one big catch-up night.What counts as a healthy sleep debt versus a concerning one?
There’s no single universal cutoff, but a small debt of a few hours across a week is common and usually manageable, while a debt that keeps growing night after night is more worth addressing. If tiredness persists despite consistent sleep, it’s worth speaking with a doctor.Do I need to fill in all seven nights to use this calculator?
No — you can leave any night blank if you don’t want to include it, and the calculator only counts nights where you entered a value. The “nights counted” figure shows exactly how many nights were used in the total.How is sleep debt different from just feeling tired?
Sleep debt is a running numerical gap between your target and actual sleep hours added up over several nights, while tiredness is a subjective feeling that can also come from stress, diet, illness, or other causes unrelated to sleep duration.What’s a realistic nightly sleep target to enter?
Most adults are generally guided toward roughly 7-9 hours a night, so many people start with a target somewhere in that range and adjust it based on how they personally feel and function.Can extra sleep on one night offset a shortfall from another night?
Within this calculator’s math, yes — because it works from a weekly total, a night well above your target reduces the overall debt figure calculated across the week, even though it doesn’t necessarily undo how you felt on the short nights themselves.Related Calculators
To figure out a good bedtime and wake-up window in the first place, try the sleep cycle calculator, and since afternoon caffeine can eat into your sleep, the caffeine half-life calculator can help you time your last cup. Late-night screen use is another common sleep disruptor worth checking with the screen time eye strain calculator.