A life is made of a few thousand weeks

Eighty years sounds like an immense stretch of time. Eighty years in weeks is about 4,200: a number that fits on a sheet of paper. It is the idea popularised by Tim Urban with his "Your Life in Weeks" calendar and by the writer Oliver Burkeman in his book Four Thousand Weeks: measure life in the unit we actually live it in, the week, to see how much room there is and what we choose to put in it.

This calculator counts the weeks lived and the weeks left according to the life expectancy you enter, and turns them into hours: how many free waking hours remain at your current pace, and how many remain for an activity you care about.

How the calculation works

You enter your age, a life expectancy, your hours of sleep per night, your working hours per week and the weekly hours you give to an activity of your choice: reading, playing music, seeing your parents, training, writing.

• Weeks lived and remaining: age and remaining years multiplied by 52.18, the number of weeks in an average year.
• Share of life lived: age divided by life expectancy.
• Free waking hours: the remaining weeks multiplied by the 168 hours of a week, minus sleep and work.
• Hours for the activity: the remaining weeks multiplied by the weekly hours you give it.

The verdict is based on the share of life lived: a percentage that does not say how long you will live, but where you stand on the calendar.

Weeks at every age

The table uses a life expectancy of 82 years, close to that of many high-income countries.

At forty you are roughly halfway. Each decade is worth just over 520 weeks: enough to change a great deal, few enough to count.

Which life expectancy to use

Life expectancy at birth is now around 73 years worldwide and above 80 in many countries, with differences between men and women and between regions. But expectancy rises with age: someone who is already sixty has, on average, more years ahead than life expectancy at birth would suggest, because they have already passed the risks of earlier ages. National statistics offices publish life tables with remaining life expectancy year by year. It is always an average: it says nothing about the individual, and the calculator uses it only as a horizon.

From weeks to the hours that matter

Weeks tell you how long the calendar is; hours tell you how much room there is for what you love. The table shows, for a 35-year-old with a life expectancy of 82, the hours remaining for an activity depending on the weekly time given to it.

Going from one to five hours a week does not change the number of weeks, but it multiplies the hours by five. The lever you control is not how long you will live, it is how you use each week.

How much free time a week holds

A week has 168 hours. Sleep takes about fifty, work for many people forty or more, and the rest is free waking time, out of which also come commuting, chores and obligations.

The calculator applies today's pace to all the remaining weeks: a simplification, because work usually ends before life does. If you are retired, or want to estimate that phase, enter zero working hours.

Occasions you can count

Many of the most important things are measured not in hours but in occasions: summers, holidays with old friends, lunches with your parents. If you see someone you love ten times a year and expect to be able to do so for another twenty years, the occasions number about two hundred. The figure is not meant to frighten: it is a reminder that some things can still be multiplied, by choosing to see them more often.

The four bands of the verdict

• Less than a quarter: the calendar is almost blank, and today's choices have the longest time to grow.
• A quarter to a half: the busiest years for many; it is worth asking which weeks you spend by choice.
• Half to three quarters: many weeks still remain, often freer ones.
• Beyond three quarters: every week weighs more, and that is exactly why it is worth more.

Using the calendar without being crushed by it

Seeing your life in weeks is striking, and the point is not anxiety but clarity. Burkeman suggests starting from here to accept that you cannot do everything and to choose consciously what to leave out. A good way to use the calculator is to repeat the count for two or three activities that matter to you and ask whether the hours left are the ones you would want.

Limits of the calculator

Life expectancy is a statistical average and not a prediction: health, lifestyle and chance matter more than any table. The calculator assumes a constant pace of sleep, work and activity for all the remaining years, which does not happen in reality. Use it as a mirror for priorities, not as a countdown.

Frequently asked questions

How many weeks does a life last?

With a life expectancy of 82 years it is about 4,280 weeks; at 90 about 4,700. That is why Oliver Burkeman speaks of four thousand weeks: a number that fits on a sheet of paper.

How are weeks lived calculated?

Multiply your age by 52.18, the average number of weeks in a year once leap years are taken into account.

Which life expectancy should I enter?

An average for your country and age, taken from your national statistics office's life tables. Remaining expectancy rises with age: someone who is sixty has, on average, more years ahead than life expectancy at birth suggests.

Why does the calculator say expectancy must exceed my age?

Because it measures the weeks that remain. If you are already past the average expectancy, use the remaining expectancy at your age, which life tables give year by year.

What is the life-in-weeks calendar?

It is a grid in which each box is a week and each row a year, popularised by Tim Urban of the Wait But Why blog. It shows at a glance how much of a life has been lived.

What are free waking hours?

The 168 hours of a week minus sleep and work, multiplied by the weeks that remain. They also include commuting and chores, so truly free time is a little less.

Does the calculator account for retirement?

No, it applies today's working pace to all the remaining weeks. To estimate the retirement phase, enter zero working hours.

What is the weekly activity for?

To turn the time that remains into something concrete: how many hours remain for reading, playing music, training or being with the people you love, at the pace you do it today.

How can I increase the hours for what I love?

Not by changing the weeks but the hours: going from one to five hours a week for an activity multiplies the time left for it by five.

Is the result a prediction of how long I will live?

No. Life expectancy is a statistical average; health, lifestyle and chance matter much more. The calculator uses it only as a horizon.

Isn't this calculation a bit grim?

It can be striking, but the aim is clarity: seeing how much room there is helps you choose better how to use it and prioritise what matters.

Can I use it at any age?

Yes, from zero to 110, with a life expectancy greater than your age. For children it shows how blank the calendar still is; for older people it is best to use remaining expectancy.