Sleep & wake-up
Sleep debt calculator
Enter how many nights, your average sleep and your target to see how much sleep debt you have built up.
Sleep debt is the gap between the sleep you need and the sleep you got, added up over time. Small amounts clear quickly; large ones take longer.
What sleep debt is
Sleep debt is the running total of sleep you miss compared with what your body needs. If you need 8 hours but average 6.5, you fall 1.5 hours short each night, and that gap adds up across the week. Most adults need 7 or more hours, so even a modest nightly shortfall can grow into a meaningful debt over several nights. This tool multiplies your nightly shortfall by the number of nights to show the total.
| Debt level | Roughly | What it feels like |
|---|---|---|
| Low | Under 3 hours | Minor; an early night or two clears it |
| Moderate | 3 to 8 hours | Noticeable focus and mood dips |
| High | Over 8 hours | Needs several steady nights to recover |
How to pay it back
You cannot erase a large debt in one marathon lie-in, and oversleeping once often just disrupts the next night. Instead, add 30 to 60 minutes of sleep per night over several days by going to bed a little earlier while keeping a steady wake time. Daylight in the morning and a consistent schedule help your body make the most of the extra hours. Preventing the debt in the first place beats repaying it.
Frequently asked questions
Can I catch up on sleep at the weekend?
Partly. A couple of extra hours can help with a small debt, but one long lie-in will not undo a large one and can throw off the following night. Spreading recovery across several nights works better.
How much sleep debt is a problem?
A few hours is minor and clears quickly. Once the total passes roughly 8 hours, many people notice lasting effects on focus, mood and energy, and recovery takes several consistent nights.
What target should I use?
Most adults do well with 7 to 9 hours. Set the target to the amount at which you wake rested without an alarm on a free day, and compare your typical nights against it.