How many weeks are in a lifetime?
A year has a little over 52 weeks: 52.18 on average, once leap years are counted. Multiply that by a lifespan and you have the number. At 79 years, the US life expectancy at birth for 2024 from the National Center for Health Statistics, it comes to about 4,120 weeks. Eighty years is 4,174. Oliver Burkeman named his book Four Thousand Weeks after the same arithmetic, and the round number has stuck because it's small enough to picture.
The calculator makes the count personal in two ways. It starts from the weeks you've already lived, and it reads the life table at your current age instead of using the at-birth average. That second part matters more than people expect. On the same 2024 table, a 30-year-old lives to 80.3 on average and a 70-year-old to 86, because reaching 70 already means you've missed the earlier causes of death that pull the at-birth figure down.
Why count a life in weeks
Tim Urban drew his life as a grid of weeks on Wait But Why in 2014, and the picture has been passed around ever since. It fits a whole life on one page, and you can put your finger on the square you're in. Years are too big to feel. Days are too small to plan more than one at a time.
A week is the right size for a plan. It has a few things that can't move, like work, classes or a standing call with your family, and a lot of hours that could go either way. You can't decide the rest of your life on a Sunday evening, but you can decide what Thursday from 7 to 8 is for, and whether your phone gets a say in it. That's also why this page ends on the current week rather than on the big number.
Where the weeks go before you plan any of them
Most of the weeks left are spoken for already. At eight hours a night, sleep takes a third of them. A full-time job until retirement takes a large share of the rest. Then the phone takes its daily average, every day. The calculator counts each of these as whole weeks: all the hours added up and divided by 168. Nobody sleeps for 800 weeks in a row, of course. It's a way to compare slices of time that are spread thin across decades.
Of those slices, the phone is the one you can change this week. Your daily average is in Settings → Screen Time → See All App & Website Activity. Spending one hour less a day on it gives you back a whole week every 168 days, because 168 days of one hour is 168 hours. If you want the phone side in more detail, Your life on your phone turns your Screen Time into years.
The tail end: time with the people you love
In The Tail End (2015), Urban counted the time he had left with his parents and found that by the end of high school he had already used most of it. The math behind that is short: how often you see someone, times the years you'll both be around. For adults who live in a different city from their parents, the first number is often a handful a year, which is why the result can land hard.
The calculator reads the life table at the other person's age, assumes you both live to the average, and keeps the visits at today's pace. It also shows the one change that moves the result most: one more visit a year adds as many visits as there are years left. A Sunday call that turns into a lunch once a quarter counts.
How the numbers are worked out
- Weeks lived: days since your birth date, divided by 7 and rounded down. With no month, the birth date is 1 July of that year.
- Life expectancy: the expectation of life at your exact age from the 2024 US period life tables (United States Life Tables, 2024, National Vital Statistics Reports, Vol. 75, No. 5; data tables), for everyone, women or men, interpolated between whole years. A period table assumes 2024 death rates stay the same for the rest of your life, so it's an average for your age, not a forecast. You can replace it with your own age in “Plan to live to”.
- Weeks left: the weeks to that age minus the weeks lived, counting the current week. Summers are the 1 July dates between today and then.
- Sleep: hours a night × 7 × weeks left ÷ 168. The default of 8 hours is a round number. The American Time Use Survey puts the US average at about 9 hours a day, but that figure includes naps and time spent trying to fall asleep.
- Work: hours a week × the weeks between now (or age 22, if you're younger) and your retirement age, ÷ 168. The default is 40 hours until 67, the Social Security full retirement age for anyone born in 1960 or later.
- Phone: your daily Screen Time × 7 × weeks left ÷ 168, at the rate you enter. Nothing is assumed if you leave it blank. A week never holds more than 168 hours, so if sleep, work and phone add up to more, the phone gets what's left.
- To plan: whatever remains. Meals, chores, getting ready and getting around come out of these weeks too.
- Visits: visits a year × the shorter of your years left and theirs, with theirs read from the same table (everyone) at their age.
It leaves a lot out on purpose: illness, holidays, changes in how you work or use your phone. The output is the scale of what you have, at the pace you're on today.
Questions people ask
How many weeks do I have left?
Count the weeks since you were born, then compare them with the weeks in an average life for someone your age. On the 2024 US life table, a 30-year-old has about 2,622 weeks left, a 50-year-old about 1,670 and a 70-year-old about 834. The calculator on this page does it from your birth year, and shows how many of those weeks sleep, work and your phone already take.
How many weeks are in a lifetime?
About 4,120 at the 2024 US life expectancy at birth of 79 years. Eighty years is 4,174 weeks, which is where the round number 4,000 comes from. A year has 52.18 weeks on average once leap years are counted.
What is the life in weeks idea?
Draw a life as a grid with one square per week, 52 squares to a row and one row per year. Tim Urban published the best-known version on Wait But Why in 2014. Oliver Burkeman's book Four Thousand Weeks (2021) is built on the same count. Seeing the whole thing on one page makes the current week easy to find.
Is the number accurate for me?
It's an average for people your age in the US in 2024, not a prediction. Health, habits, income and where you live all move it, and other countries have their own tables. If you'd rather plan to a different age, open "Change the assumptions" and set "Plan to live to".
Do you store what I enter?
No. The math runs in your browser and there's no account. A shared link carries only two numbers, your weeks left and the weeks to plan. The name of the person you add never leaves your screen.