Article
How much of your life do you spend sleeping?
Sleeping 8 hours a day means spending a third of your life asleep. In an 80-year life that is almost 27 years. Here we look at the numbers and why that time is far from wasted.
The years we sleep, by hours of sleep
To calculate how much of life is spent sleeping, just divide the hours of sleep by 24 and multiply by the years of life. For an 80-year life:
| Hours of sleep per day | Share of life | Years asleep (out of 80) |
|---|---|---|
| 6 h | 25% | 20 years |
| 7 h | 29.2% | ≈ 23.3 years |
| 8 h | 33.3% | ≈ 26.7 years |
| 9 h | 37.5% | 30 years |
Put another way: each daily hour of sleep amounts, over an 80-year life, to about 3.3 years of sleeping time.
Why sleep is not wasted time
It is easy to see sleep as a tax on free time, but during rest the body and brain carry out essential tasks:
- Memory consolidation: what we learn during the day is organised and fixed while we sleep.
- Emotional regulation: sleeping too little is usually associated with more irritability and poorer stress management.
- Physical recovery: rest takes part in tissue repair and in the working of the immune system.
- Performance and attention: an extra hour of sleep usually more than makes up for the time you "save" by sleeping less.
How many hours are recommended
Scientific societies specialising in sleep medicine recommend that adults sleep at least seven hours a night, although needs vary from person to person: some do well with seven hours and others need nine. Teenagers and children need more. If you habitually sleep little and feel exhausted, it is worth discussing it with a healthcare professional; this website does not provide medical advice.
Simple habits to sleep better
- Keep regular schedules, including at weekends.
- Cut back on caffeine from the afternoon onwards.
- Avoid bright screens in the hour before bed.
- Aim for a dark, quiet and cool bedroom.
- Do not eat too much at dinner and leave some time before going to bed.
Sleep within your time breakdown
In Sandglass, sleep is the first activity you can adjust: you move the hours control and instantly see how many months of your remaining life are split between sleeping, working or using your phone. It is a very visual way to understand that the hours of the day are a limited budget.
Sleep cycles
Sleep is not a uniform phase: it is organised in cycles of about 90 minutes (the exact length varies between people and across the night) alternating light sleep, deep sleep and REM sleep. A full night is made up of four to six cycles. Waking up at the end of a cycle usually feels easier than doing so in the middle of a deep phase, and that is where the popular advice comes from to work out bedtime in multiples of 90 minutes, plus the time it takes to fall asleep (about 15 minutes on average).
You can do that calculation with the sleep calculator: enter the time you want to get up and it suggests bedtimes, or the other way round.
How much to sleep by age
General recommendations from organisations specialising in sleep put approximate needs like this:
| Age | Indicative hours of sleep |
|---|---|
| School-age children (6-13 years) | 9 to 11 hours |
| Teenagers (14-17 years) | 8 to 10 hours |
| Adults (18-64 years) | 7 to 9 hours |
| People over 65 | 7 to 8 hours |
These are indicative ranges for healthy people; if you have persistent sleep problems, the right thing to do is consult a health professional.
Sleep debt
Sleeping one hour less each night does not seem like much, but it adds up: seven hours a week and about 30 hours a month, almost four full nights of sleep. Making it up with a long nap or by sleeping a lot at the weekend helps in part, though it does not fully make up for the effects of continued deprivation, and it also throws off the following week's routines.
Naps: yes, but in moderation
A short nap of about 20 to 30 minutes can improve alertness and mood without interfering too much with night-time sleep. Long or very late naps can make it harder to fall asleep at night. The best thing is to try what works for you and keep a certain regularity.
What to do with these numbers
If you sleep about seven hours, you will sleep about 23 years of an 80-year life; with nine hours it will be 30. The point is not to cut that figure, but to understand that sleeping well is the foundation for the rest of the hours of the day: with good rest, waking time is more productive and more enjoyable.
Want to see your own figures? Sandglass calculates your time in seconds, right in your browser.
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