Sleep Debt Calculator
Log your sleep over the past 7 nights to discover exactly how much rest you owe your body — and get a personalised plan to recover it.
Last updated: April 2026
Set Your Target
Your recommended sleep target: 8 hours per night
Leave blank to use the recommended target.
Log Your Week
What is Sleep Debt?
Sleep debt is the cumulative shortfall between the sleep your body needs and the sleep you actually get. It is calculated on a rolling basis — typically over the last 7 days, as your brain primarily weights recent sleep history.
If you need eight hours of sleep but only get six, you do not just miss out on two hours of rest. You accumulate two hours of sleep debt. Do this for five nights, and you are carrying a 10-hour deficit. This is a real, measurable physiological state, not just the subjective feeling of being tired.
How the Sleep Debt Calculator Works
The calculator asks you to enter your actual sleep duration for the last seven nights. It compares this against your recommended sleep target based on your age group (or a custom target you set).
It then subtracts any nights where you slept more than your target, giving you a net sleep debt figure in hours. From this, it generates a personalised, mathematically precise recovery plan showing exactly how many nights it will take to pay back the debt at different paces.
What Sleep Debt Does to You
The effects of sleep debt are profound and cumulative. As your debt increases, your reaction time deteriorates significantly. Studies have shown that severe sleep debt produces cognitive impairment comparable to alcohol intoxication.
It also affects your mood, increasing irritability and emotional reactivity. Your decision-making and risk perception become impaired — often without you realising it. Physically, sleep debt suppresses immune function, making you more susceptible to common illnesses.
The most dangerous aspect of chronic sleep debt is that you stop noticing it. After 10 days of losing an hour of sleep a night, you might think "I'll be fine," but objective tests will show your performance has dropped substantially.
Can You Recover from Sleep Debt?
The short answer is: partially, yes — but not by attempting an hour-for-hour weekend catch-up.
You have three main recovery levers: extending your night sleep, taking a 90-minute nap, and maintaining a more consistent schedule. Research shows that full cognitive recovery from chronic sleep loss takes longer than the loss took to accumulate.
Weekend lie-ins are a common strategy, but they don't fully fix the problem. Sleeping until noon on Sunday creates "social jetlag," pushing your circadian rhythm out of sync and making it much harder to fall asleep on Sunday night and wake up on Monday morning.
A Realistic Recovery Plan
Recovering from sleep debt requires a structured approach, not just one long sleep.
- Stop accumulating: The first step is to stop adding to the debt. Fix your bedtime so you are consistently getting your target hours.
- Add 30–60 minutes per night: Rather than sleeping in for four extra hours on a Saturday, go to bed 30 to 60 minutes earlier every night for a week.
- Add a 90-minute weekend nap: If you need a larger boost, a 90-minute nap on the weekend allows you to complete a full sleep cycle without disrupting your night-time rhythm as much as a morning lie-in.
- Re-measure: After 7 days of your recovery plan, use the calculator again to track your progress.