Free sleep calculator
Sleep Debt Calculator
Add up a week of short nights into one number, then a concrete plan — naps or an earlier bedtime — to pay it back.
Your weekly sleep debt
How to pay it back
This is arithmetic on the total, not a guaranteed repayment schedule — real recovery from a sleep deficit isn't perfectly 1:1 (see the caution in the sources below). Treat both options as a starting plan, and prefer the gradual one.
Not medical advice. This tool gives a general estimate for informational purposes only — it does not replace professional judgment. If you're concerned, contact a doctor right away. This adds up reported sleep duration against a population-average target — it can't see sleep quality, and it isn't a diagnosis of sleep deprivation. If you're regularly exhausted, can't fall or stay asleep, or think you might have a sleep disorder, talk to a doctor or sleep specialist.
How this is calculated & sources
The formula: weekly sleep debt = the sum, across your last 7 nights, of
max(0, target hours − actual hours slept that night). Nights below target add to the
total; nights at or above target add zero rather than a negative number. That's a deliberate
choice, not an oversight: sleep debt is framed here as "how much catch-up sleep you're owed," and
one good night can't retroactively erase an earlier short one any more than a bank balance rises
because you could have overdrawn less on a different day. Oversleep still shows up in the average
line above the result, it just doesn't offset debt.
Nightly target by age: the per-night target comes from the National Sleep Foundation's 2015 expert-consensus sleep duration recommendations (Hirshkowitz et al., Sleep Health, 2015 — the same panel Sleep Foundation summarizes here, and the same source hearthcalc.com's baby-sleep-schedule-calculator uses for its own age bands): young adults 18–25 and adults 26–64 are both recommended 7–9 hours; older adults 65+ are recommended 7–8 hours. A recommended range doesn't reduce to one number on its own, so this calculator uses the midpoint of each band's range (8h for the two adult bands, 7.5h for 65+) as the single nightly target — a product decision, not a sourced figure in itself, made so the debt math has one number to subtract from each night. The full NSF range for your selected band is shown next to it above.
The recovery plan: the definition of sleep debt ("the difference between the amount of sleep someone needs and the amount they actually get"), and the two recovery approaches shown above — short naps and gradually shifting bedtime earlier — come from Sleep Foundation's "Sleep Debt: The Hidden Cost of Insufficient Rest", which specifically recommends short 10–20 minute naps (this calculator's arithmetic uses the more conservative 20-minute end — the same length hearthcalc.com's own Nap Calculator recommends to avoid grogginess) and increasing sleep time gradually, 15–30 minutes at a time (this calculator uses the smaller, more sustainable 15-minute end), rather than trying to erase a deficit in one long lie-in. The same source cautions that real recovery isn't instant — it can take up to four days to recover from one lost hour of sleep, and up to nine days to fully clear a build-up of debt — so both numbers above are a starting arithmetic breakdown of the total, not a guaranteed day-by-day repayment schedule.
The wedge, stated plainly: this calculator doesn't just report a number — it turns that number into two concrete next steps on Hearth's own sleep tools: the Nap Calculator for the timing of a recovery nap, and the Sleep Cycle Calculator for a bedtime that also lands on a full 90-minute sleep cycle.
These are general guidelines built from population averages and self-reported hours, not a measurement of your actual sleep quality or a clinical diagnosis. If short sleep is a regular pattern for you, or you suspect a sleep disorder, that's worth raising with a doctor.