The average human lifespan
4,000 weeks
That's it. That's the whole thing — school, work, love, summers, Tuesdays. The number sounds impossible until you see it drawn.
4,000 weeks is 76.7 years — precisely 76 years, 7 months and 28 days. The math: 4,000 × 7 = exactly 28,000 days, divided by the average year of 365.2425 days = 76.66 years, or about 920 months (672,000 hours, if you like your mortality in hours). If you got 76.9 by dividing by 52, that's the common shortcut — a year actually has 52.1775 weeks, which is where the small difference comes from. That's why the number stands in for a lifetime: world life expectancy sits within a few years of it.
| Weeks | Years | As a life |
|---|---|---|
| 3,000 weeks | 57.5 years | mid-fifties |
| 3,500 weeks | 67.1 years | retirement age, roughly |
| 3,652 weeks | 70 years | a 70-year life |
| 4,000 weeks | 76.7 years | the famous round number |
| 4,174 weeks | 80 years | an 80-year life |
| 4,696 weeks | 90 years | a 90-year life |
| 5,000 weeks | 95.8 years | past almost everyone |
Put this on your desktop.
The Mac app sets this exact calendar as your wallpaper and re-draws it every midnight — the countdown ticks down by itself.
The idea
Oliver Burkeman's Four Thousand Weeks begins with a blunt observation: the average life is absurdly, insultingly finite — and pretending otherwise is how we lose it. Tim Urban's essay Your Life in Weeks made the same point with a picture. A life isn't an ocean of time; it's a grid you can fit on one sheet of paper.
The strange thing is what the picture does. People expect it to feel morbid. Instead it feels clarifying — suddenly this week, the one you're in, is visibly one of a limited edition.
See your own
The calculator draws your 4,000 weeks free in ten seconds. The Mac app keeps the picture on your desktop, marking off one circle every Monday, forever.
The number, checked
Four thousand is the round version: 4,000 weeks works out to 76.7 years (28,000 days), and world life expectancy sits within a year of it. An 80-year life is about 4,174 weeks; 90 years is 4,696. Pick your own horizon on the life expectancy calculator and the grid redraws to match — the argument doesn't depend on the digit.
Questions
How many years is 4,000 weeks?
4,000 weeks is 76.7 years — precisely 76 years, 7 months and 28 days. The math: 4,000 × 7 = 28,000 days, divided by the average year of 365.2425 days = 76.66 years.
Is 4,000 weeks 77 years or 80 years?
Both answers are out there, for different reasons. Dividing 4,000 by 52 gives 76.9, but a year has 52.1775 weeks, so the true conversion is 76.7. The "80 years" version comes from Oliver Burkeman's framing — if you live to 80 you get about 4,000 weeks — but 80 years is really 4,174 weeks; 4,000 is the round-number version of a 76.7-year life.
How many weeks are in the average life?
About 3,800. World life expectancy is roughly 73 years, and 73 × 52.1775 ≈ 3,809 weeks. "4,000 weeks" rounds that up to something memorable — the argument survives the rounding either way.
How many weeks is 80 years? And 90?
80 years is 4,174 weeks; 90 years is 4,696. In the other direction, 70 years is 3,652 weeks. Pick your own horizon on the life expectancy calculator and the grid redraws to match.
How do I see my own 4,000 weeks?
The life in weeks calculator draws your grid free in ten seconds — every week you've lived filled in, every week ahead left open. No signup, nothing stored.