Turn your date of birth into total days lived, weeks lived, and the weekday you arrived on. Instant, free, no signup.
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Most people know their age in years. Fewer people know their age in days — which is a shame, because the number is way more interesting. A ten-thousand-day birthday lands somewhere in your late twenties. Twenty thousand days is right around age fifty-five. The math is simple, but nobody thinks about it until they see it: your life measured in single, ticking days.
The calculator above converts your date of birth to today into an exact count of days. Not an estimate. Not "roughly" anything. It uses the difference in milliseconds between the two dates, divides by 86,400,000 (the number of milliseconds in a day), and floors the result. Leap years are counted correctly — the extra day in February shows up as an extra day in your total, no adjustment needed.
One thing you might not have thought about: the weekday you were born. Everyone knows their birthday, but ask most people what day of the week that was and you'll get a blank stare. The tool tells you that too. There's a small algorithm called Zeller's congruence that will spit out the weekday for any date in history, but JavaScript's built-in Date object handles it out of the box, so we let it do the work. If you were born on a Tuesday, that's what the tool will say.
The weeks lived figure is just the days count divided by seven, floored. It's a useful number if you're thinking about how you've spent your time. Tim Urban wrote a much-passed-around essay called "Your Life in Weeks" that showed a person's life as a grid of about 4,680 boxes — roughly ninety years. Seeing your age in weeks makes the grid feel a lot more concrete.
If you want your age in even smaller units — hours, minutes, seconds — those are on the main age calculator. And if you're curious how many days until your next birthday, the birthday countdown handles that.
You don't count by 365 at all. The correct way is to compute the millisecond difference between the two dates and divide by 86,400,000 (ms per day). Leap seconds and DST are ignored because they don't add up to a full day, but the extra February 29th is captured automatically.
The calculator above tells you at the same time it computes your age. Under the hood it's using the Gregorian calendar's rules — the same rules that mean a Tuesday in 1995 was the same weekday as a Tuesday in 2023. If you're curious about the math, look up Zeller's congruence.
About 10,957. Thirty years is either 10,957 or 10,958 days depending on how many leap years fall in the interval and where in the year you start. The tool computes the exact answer from your actual birthday.
Jeanne Calment (France, 1875–1997) lived to 122 years and 164 days — that's 44,724 days. The tool caps at whatever you enter, but nobody has verifiably crossed 45,000 days yet.
We wrote a playful guide covering every weird way to count your age — units, cultures, and the birthday paradox.
Read the age guide →