Tool · Sleep & Recovery
Sleep Debt Calculator
How much sleep you actually owe yourself, based on the last 7 nights. With a recovery plan that doesn't pretend you can fix a month of 5-hour nights with one Saturday lie-in.
Last 7 nights
Most recent night first. Be honest — round numbers lie.
What this actually does
It adds up how many hours of sleep you missed against the lower end of an evidence-based target for your age, then divides by a recovery rate that doesn't pretend you can sleep 14 hours on Saturday and call it fixed. The recommended target uses the National Sleep Foundation consensus (Hirshkowitz et al., 2015): 7–9 h for adults 18–64, 7–8 h for 65+, 8–10 h for teens, 9–11 h for school-age children.
The "debt" definition is conservative. We use the lower bound of your target, not the midpoint, so a 7.5 h night at age 34 counts as zero debt even though 7.5 isn't perfect. If you sleep more than your target, we don't credit you a surplus — banks don't either.
Who it's for
People who suspect they're chronically under-sleeping but have no number to attach to the feeling. People tracking down the cause of an afternoon slump. Anyone who's been told "just sleep more" without anyone showing them the math.
If you already track sleep with a wearable (Oura, Whoop, Apple Watch), this will be less granular than what you have. It's the calculator version — quick, manual, honest.
Limitations
Self-reported sleep is usually optimistic by 30–60 minutes. If you want to be hard on yourself, add 0.5 h to the deficit for each night you "slept about 6" without remembering. The tool doesn't know your sleep efficiency — whether those 7 hours were really 7 hours of sleep or 8.5 hours in bed with 90 minutes of waking.
The recovery plan is a pace, not a guarantee. If your debt is enormous and you're sleeping poorly, the right next step isn't a calculator — it's a clinician.
How to read the chart
Each bar is one night. The moss bar is what you slept; the light moss line is the recommended floor for your age. Where the actual is shorter than the recommended, the orange deficit shows how much you under-shot. A pattern of mostly-orange is chronic; a single orange spike is a bad night.
FAQ
Why the lower end of the target, not the middle?
Two reasons. One: it stops you from gaming it by claiming 8.5 h when you slept 7. Two: most adults who feel well-rested sleep closer to 7 than 9, so the lower bound is the fairer baseline for "did you sleep enough?"
Why can't I just sleep 12 hours on Saturday?
Because sleep isn't a savings account. Most research suggests the body recovers more from consistent bedtimes than from occasional marathons, and a 4-hour Saturday lie-in often wrecks Sunday night's sleep. The recovery plan tops out at 1 extra hour per night for a reason.
What counts as a "night"?
The main sleep period — the longest stretch you slept, even if it was a split night. If you slept 5 h at night and 2 h in the afternoon, type 7. We treat naps as recovery budget, not debt, and the recovery plan suggests when to use them.
Why no "sleep bank" for over-sleeping?
Because the evidence doesn't support it. The body adapts to consistent sleep, not stockpiled sleep. A 10-hour Saturday doesn't make Monday's 6-hour night easier; in some studies it makes it harder by shifting your circadian window.
What are the common mistakes when using Sleep Debt Calculator?
Most common mistakes come down to four habits: entering 20 when the field expects 0.2 because the field is a percentage; leaving a field blank and accepting the default without checking what it stands for; changing one input and reading a result that was calculated before the change; and quoting the output as an exact figure when the page describes it as a reference estimate. Press calculate again after any edit, and treat the number as a reference point rather than a final answer.Advertisement