Late nights add up. Find your sleep debt and how long it takes to repay.
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Sleep debt is the difference between the sleep you need and the sleep you get, added up over days. One week of 6-hour nights when you need 8 leaves a 14-hour debt — almost two full nights.
Enter the hours you slept each night. The calculator totals the debt, shows your average, and plans a recovery by sleeping a little longer each night rather than with one long lie-in.
| Hours of sleep you need | 8 hours |
| Monday night | 6 hours |
| Tuesday night | 6.5 hours |
| Wednesday night | 5.5 hours |
| Thursday night | 6 hours |
| Friday night | 7 hours |
| Saturday night | 9 hours |
| Sunday night | 8 hours |
| Extra sleep you can add a night | 1 hours |
| Your sleep debt this week | 8 hours |
| Average sleep | 6.9 hours a night (you need 8) |
| Like missing | 1 full nights |
| To repay it | sleep 1 hour more for 8 nights |
| Over a year at this rate | 417 hours (52 nights) |
| How it can feel | Mild tiredness, lower focus and more cravings |
Debt 8 hours.
| Hours of sleep you need | 8 hours |
| Monday night | 5 hours |
| Tuesday night | 5 hours |
| Wednesday night | 4.5 hours |
| Thursday night | 5 hours |
| Friday night | 5 hours |
| Saturday night | 7 hours |
| Sunday night | 8 hours |
| Extra sleep you can add a night | 1 hours |
| Your sleep debt this week | 16.5 hours |
| Average sleep | 5.6 hours a night (you need 8) |
| Like missing | 2.1 full nights |
| To repay it | sleep 1 hour more for 17 nights |
| Over a year at this rate | 860 hours (108 nights) |
| How it can feel | After a week under 6 hours, reaction times are as slow as after a full night awake |
16.5 hours.
Short-term debt, yes: a few extra hours over several nights helps you recover alertness. Long-term sleep loss over months is harder to undo, so regular sleep matters more than catching up.
A small lie-in is fine, but sleeping 2–3 hours later shifts your body clock ('social jet lag') and makes Monday harder.
Yes, naps reduce sleep debt. Keep them short (20 minutes) or a full 90-minute cycle, and not too late in the day.