Can you catch up on sleep on weekends? What the numbers say
Want to count your own week night by night? The sleep debt calculator adds up the hours you are short.
The week in numbers
Put in your own times to see both numbers.
Fill in when you fall asleep and wake on workdays and on the weekend. The calculator adds up the hours you are short over 5 workdays, the way the sleep debt calculator does, then sets the weekend's extra hours against them. It also measures how far the middle of your sleep moves on the weekend, the gap the social jet lag calculator reports. The starting need is 7 hours, the bottom of the CDC range for adults.
Your week: the debt and the clock
Three weeks against a 7-hour need: the debt and the clock
| Week | Short by Friday | Middle of sleep moves | Weekend extra | Left on paper | Weeknights | Weekend nights |
|---|---|---|---|---|---|---|
| Steady | none | no change | none | even | 11:30 PM to 6:30 AM (7 h) | 11:30 PM to 6:30 AM (7 h) |
| Short weeknights, lie-ins | 2 h 30 min | 2 h later | 3 h | 30 min over | 12:00 AM to 6:30 AM (6 h 30 min) | 1:00 AM to 9:30 AM (8 h 30 min) |
| Shorter weeknights, long lie-ins | 5 h | 3 h later | 4 h | 1 h short | 12:30 AM to 6:30 AM (6 h) | 2:00 AM to 11:00 AM (9 h) |
Why the sum is not the whole answer
In the second week, 6 h 30 min a night leaves you 2 h 30 min short by Friday, and two 8 h 30 min weekend nights add 3 h: on paper, the debt is paid. NIOSH's training for nurses, which gives the sleep debt arithmetic, also warns against reading it that way: “It is risky to build up a sleep debt and try to pay it off later.” (source) It explains that sleepiness may return to normal after a day or two of recovery sleep while performance can still be below normal. It also says you don't necessarily need to pay back hour for hour, because the body sometimes sleeps more soundly to pay down the debt.
The hours are still worth counting, and the sleep debt calculator counts them night by night. But NIOSH's conclusion is about the pattern: “getting adequate sleep on a regular basis, rather than episodically, is important.” (source)
What the lie-in does to your body clock
The second number in the calculator is the move in the middle of your sleep. Its research name is social jetlag (Roenneberg et al., Current Biology): the gap between the midpoint of sleep on free days and on workdays. In the second week the middle of your sleep moves 2 h later on the weekend, the middle band in our calculator. In the third week it moves 3 h. That later clock can carry into the week: in the Depner study below, the body clock was still running later once the short weeknights began again.
The more hours a lie-in gives back, the further it usually moves the clock. Going to bed earlier on a weeknight adds hours and leaves the morning where it was.
What two laboratory studies found
In a 2019 laboratory study by Depner and colleagues, healthy young adults spent a 5-day working week on 5-hour nights, then had 2 days to sleep as long as they liked, then went back to short nights (14 people in that group). Over the weekend they slept only about 1.1 hours more than at baseline. After the weekend their body clock was later, and the study found that the weekend did not stop the changes in how their bodies handled sugar. The authors conclude that “weekend recovery sleep is not an effective strategy to prevent metabolic dysregulation associated with recurrent insufficient sleep.” (source)
In a 2003 laboratory study by Van Dongen and colleagues, 48 healthy adults took part, and some of them spent 14 days with 6 or 4 hours in bed a night. In those groups, performance on attention and thinking tests fell steadily, until it matched up to 2 nights with no sleep at all. Their own sleepiness ratings rose only a little, and the researchers found they were largely unaware of how far their performance had dropped. Both studies were small and run in a laboratory, so read them as what can happen. Your own week may go differently.
Getting more sleep without moving the morning
If the calculator shows a debt every week, the weeknight bedtime is the one to move: it adds hours and keeps your clock in place. The sleep calculator gives bedtimes that end on a full sleep cycle for your alarm, and the one-hour wind-down plan times the evening back from that bedtime. A weekend lie-in that stays short keeps the move in the middle of your sleep small.
What the hours don't measure
The table and the calculator count hours asleep against one need figure; they cannot measure how rested you are. The two studies were small laboratory studies of healthy young adults, and the move in the middle of your sleep measures timing only. It says nothing about health. The need of 7 hours is the bottom of the CDC adult range; your own need may be higher.
See a doctor if you are sleepy during the day even after enough sleep, if you snore loudly, or if you regularly take more than 30 minutes to fall asleep. This guide is general information, not medical advice: read our disclaimer.
Frequently asked questions
Can you catch up on sleep on weekends?
In hours, partly: a weekend lie-in can add back what the week took. NIOSH warns that performance can stay below normal even after sleepiness recovers, and in a laboratory study a recovery weekend added only about 1.1 hours and did not prevent the changes in how the body handled sugar.
How much sleep debt does a lie-in pay back?
In the table's second week, two 8 h 30 min nights add 3 h against 2 h 30 min short over the weekdays. NIOSH says you do not necessarily need to pay back hour for hour.
Is an earlier bedtime better than a lie-in?
It adds the same hours without moving your wake-up time, so the middle of your sleep stays where it is. The sleep calculator gives bedtimes for your alarm.
Does a nap count toward the debt?
The sleep debt arithmetic counts all sleep. The nap planner times a nap so that it leaves tonight's bedtime clear.
Sources
- CDC/NIOSH — Training for Nurses, Module 2: Sleep Pressure (sleep debt)2020 · read on
- Roenneberg et al., Current Biology — Social Jetlag and Obesity (full text)2012 · read on
- Depner et al., Current Biology — Ad libitum Weekend Recovery Sleep Fails to Prevent Metabolic Dysregulation during a Repeating Pattern of Insufficient Sleep and Weekend Recovery Sleep (abstract, PubMed)2019 · read on
- Van Dongen et al., Sleep — The cumulative cost of additional wakefulness (abstract, PubMed)2003 · read on
- CDC — About Sleep (recommended hours by age)2024 · read on
- CDC/NIOSH — Training for Nurses, Module 6: Do You Have Symptoms of a Sleep Disorder?2020 · read on