How to use
- Enter the bedtime and wake-up time for each night this week. If you can't remember a night, clear its time and it is skipped.
- Tick "Day off next day" for nights before weekends and holidays.
- Pick an age; each night is compared with the minimum recommended for that age.
- Read the average, the total you're short and your social jet lag.
Options explained
- Sleep debt
- The amount you fell short of the recommended minimum, added up over the nights. If an adult needs at least 7 hours and sleeps 6 on five nights, that's 5 hours of debt.
- Social jet lag
- How far your mid-sleep on days off is from your mid-sleep on work days. The idea comes from a 2006 study by Wittmann, Roenneberg and colleagues. Your work schedule and your body clock don't match, so every weekend is like a trip across time zones.
- Mid-sleep
- The point halfway between falling asleep and waking. Asleep at midnight and up at 7 gives 3:30 am. It shows how early or late your sleep runs better than bedtime alone.
Reading the results
- Average per night: across every night you filled in, with nights before work days and nights before days off shown separately.
- Nights short: how many nights fell below the recommended minimum for the age you picked, and how much sleep you missed in total.
- Catching up: how much more than the minimum you slept before days off. A lot of catching up usually means a lot of debt during the week.
- Social jet lag: how much later your mid-sleep is on days off than on work days.
The dashed line on the chart is the recommended minimum; bars below it are nights you didn’t get enough.
How much you should sleep
Adults need at least 7 hours, 6–13-year-olds 9–11 hours and 14–17-year-olds 8–10 hours. For the full table by age, and to time your bedtime by sleep cycles, see the sleep calculator. If you’re sleepy during the day, the nap calculator tells you how long to nap.
Frequently asked questions
Can I catch up on sleep at the weekend?
It eases tiredness but doesn't undo the debt. In a 2019 study by Depner and colleagues, people who slept 5 hours on weeknights and as long as they liked at weekends still had worse insulin sensitivity. Going to bed half an hour earlier every night helps more than sleeping in.
How much social jet lag is a lot?
Under an hour is fairly regular. Over an hour and Monday mornings tend to be hard. Getting up at the weekend not much later than usual, and napping if you need to, keeps it down.
How is time slept worked out?
From bedtime to wake-up time, including any time lying awake. If you take a long time to fall asleep or are awake for a while in the night, enter roughly when you fell asleep instead.
I feel fine on 6 hours. Do I really need 7?
The recommendations are for most people. Someone who has been short of sleep for a long time often gets used to feeling tired and stops noticing. Try sleeping a bit more every night for a week or two and see whether your days feel different.
Privacy
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