Exhausted Businessman At Desk

Everybody needs sleep. In fact, sleep is so important that neglecting it for a few days can have important consequences.

Aside from making you grumpy and irritable, lack of sleep decreases alertness, resulting in an increased risk of having an accident while driving or performing other tasks that similarly require your full attention.

Sleep deprivation can also lead to stress, obesity, poor memory, increased vulnerability to infection and a generally decreased quality of life.

One way of trying to gauge if you are getting enough sleep is the concept of sleep debt. So do you know how much your sleep debt is?

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What Is Sleep Debt?

Most adults require 7 to 9 hours of sleep per night[1]. The concept of sleep debt originates from the theory that by skipping a few hours of sleep on a regular basis, your body actually accumulates missing hours of sleep – the sleep debt.

Losing an hour of sleep every day of the week would theoretically cause you to accumulate a seven-hour sleep debt that you can only “repay” by sleeping seven extra hours at some point.

However, there are some unwritten rules about sleep debt. It is generally thought that you should not repay your sleep debt more than a couple of hours at a time. If your sleep debt is 8 hours, you cannot sleep 16 hours on Saturday and consider the problem solved.

Generally, it is thought best to add an extra hour or two of sleep over several days. While people with a large sleep debt might feel more alert after a great night of sleep, the effect is only temporary and the consequences of chronic sleep deprivation persist.

It’s also important to keep in mind that while sleep debt is certainly a phenomenon you can experience, it is not as mathematically precise as balancing your checkbook.

While the concept of sleep debt was first coined some 50 years ago, it is one that continues to evolve as scientists carry out additional studies.

Some researchers have gone as far as suggesting that an individual who does not pay off their sleep debt promptly and gradually may experience reduced alertness and wakefulness permanently.

While further studies are still needed to verify this claim, the message from scientists is unified across the board: pay off sleep debt as soon as possible, or avoid it altogether by banking extra sleep hours in advance when you know you’ll be getting fewer hours of rest than your body needs.

Calculating Your Sleep Debt

Calculating your sleep debt can be tricky. It could be as straightforward as “one lost hour of sleep equals one hour of sleep debt”.

However, considering the fact that we should be sleeping half an hour for each hour of wakefulness in a day (8 hours of sleep for 16 hours of wakefulness), losing an hour of sleep could translate to an hour and a half of sleep debt.

This theory is interesting because it takes into account the fact that extra hours of wakefulness due to lost sleep also need to be accounted for when calculating true sleep debt.

For example:

Sleep needed: 8 hours Hours spent awake: 16 hours Sleep/wake ratio: 1:2
Hours slept last night: 6 hours Hours spent awake: 18 hours Sleep/wake ratio: 1:3


Notice how, by losing 2 hours of sleep one night, the ratio of sleep hours to waking hours shifts from 1:2 to 1:3. To maintain the natural 1:2 ratio, you would technically need 9 hours of sleep to counter 18 hours of wakefulness.

However, in the example above, you only slept for 6 hours. According to the theory, it means that your sleep debt from losing 2 hours of sleep one night needs to be made up with 3 extra hours of sleep. It may explain why sleeping in for two extra hours on Saturday and Sunday is not enough to make up for the hour of sleep you lost every night of the previous week.

Tips On Repaying Your Sleep Debt

The first step in repaying your sleep debt is acknowledging that sleep is not a luxury. Many people cut into their hours of sleep when they need extra time to accomplish tasks, resulting in the accumulation of a significant chronic sleep deficit.

If your sleep debt is only a few hours (for example staying up late to study for an exam), you can make up for it by sleeping in for an extra hour or two on the weekend and going to bed an hour earlier the following week.

If your sleep debt is the result of several weeks or months of sleep deprivation, consider going to bed earlier for several weeks until your debt is paid off. If you can afford it, take a vacation with the goal of sleeping until you wake up naturally every day. At first, you may sleep for 10 or more hours, but this will gradually stabilize as your sleep debt decreases.

Once your sleep debt is paid off, avoid accumulating another one.

Use the sleep debt calculator to figure out how many hours of sleep you need to feel your best, and make sure you fit enough sleep hours into your schedule. Going to bed and waking up at regular hours will ensure that you get the amount of sleep you really need.