Lifetime Sleep Calculator

How it is calculated

Enter your average sleep per night in hours, your current age in years and the life expectancy you want to assume. The tool turns the sleep into a share of the day, share = hours ÷ 24, and applies it to two spans: years so far = age × share and years in total = life expectancy × share. The third result, total days asleep, is life expectancy × 365.25 × share. The second number covers the whole life, not only the years still ahead, so subtract the first to get the remainder. Years use one decimal. Impossible entries give no result: nightly sleep must be above 0 and at most 20 hours, age must be between 0 and 120, and life expectancy must be above 0, at most 120 and not below your age. Sleep is assumed constant across your whole life, although babies and older adults sleep differently.

Common mistakes

• Reading the second figure as the sleep still to come. It is the sleep over the entire life expectancy, so the remaining amount is that figure minus the years so far.
• Entering the time spent in bed instead of time actually asleep. If you lie in bed for 8 hours but sleep 7, enter 7.
• Using a minutes value such as 450 in the hours field. The field takes hours, so 7.5 is correct, and anything above 20 gives no result.
• Entering a life expectancy below your current age. The tool gives no result; the figure must be at least your age.
• Treating the result as a forecast. It multiplies one average over decades, and your sleep need changes with age, illness and life stage.