Age Calculator
Enter a date of birth (or any past date) to find the exact age in years, months, weeks, and days. The calculator also shows your total days and hours lived, and how long until the next birthday.
How the calculation works
Calculating age sounds straightforward, but calendar arithmetic is trickier than it appears. Months have different lengths, leap years add an extra day every four years (with century-year exceptions), and what counts as a complete year depends on whether the anniversary date has passed in the current year.
The calculator follows the most common convention: it counts complete years first, then remaining complete months, then remaining days. A person born on 15 March who checks their age on 10 May has had their birthday this year, so the months count forward from March. Someone checking on 10 January has not had their birthday yet, so months count from the previous March.
Age milestones in days and hours
| Age | Approx. days | Approx. hours |
|---|---|---|
| 1 years old | 365 | 8,760 |
| 5 years old | 1,826 | 43,824 |
| 10 years old | 3,652 | 87,648 |
| 18 years old | 6,574 | 157,776 |
| 21 years old | 7,665 | 183,960 |
| 30 years old | 10,958 | 262,992 |
| 40 years old | 14,610 | 350,640 |
| 50 years old | 18,263 | 438,312 |
| 60 years old | 21,915 | 525,960 |
| 70 years old | 25,568 | 613,632 |
Figures are approximate — actual values vary by leap years in each person's lifetime.
Common questions
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The calculator finds the number of complete years between your birth date and today, then counts the remaining full months, then the remaining days. It mirrors how most people would count their age in everyday speech, accounting for the different lengths of months and leap years.
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Enter your date of birth above and the calculator will show your exact age in total days. As a rough guide, a 25-year-old is around 9,125 days old; a 40-year-old is around 14,610 days old; a 60-year-old around 21,915 days old — though leap years make the precise figure vary.
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Yes. The calculator uses JavaScript Date objects which handle leap years, varying month lengths (February 28 vs 29 days, months with 30 vs 31 days), and daylight saving time transitions automatically.
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Absolutely. You can enter any past date as the start date — the founding of a company, the date a building was constructed, the launch of a product, or any historical event — and calculate exactly how long ago it was.
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The calculator handles this correctly. In non-leap years, the anniversary is treated as 28 February for the purposes of calculating complete years, which is the convention used in most legal and administrative contexts.