Age Calculator
Calculate exact age in years, months and days between a date of birth and any date — plus total days, weeks, months, day of the week born, and a countdown to the next birthday.
Input
Leave blank to use today's date
Output
| Metric | Value |
|---|---|
| No data yet | |
Guides
The Age Calculator works out exactly how old someone is — in years, months, and days — between a date of birth and any reference date. It also converts that age into total months, weeks, and days, tells you which day of the week the birth date fell on, and counts down to the next birthday.
How it works
Age is calculated the way a calendar actually works, not by dividing the number of days lived by 365.25. The tool walks the calendar year by year and month by month, accounting for the real length of every month (28, 29, 30, or 31 days) and for leap years, so the years/months/days figure is exact for any pair of dates — not an approximation.
How to use it
- Enter a Date of Birth.
- Optionally enter an As of Date — the date you want the age measured against. Leave it blank to measure age as of today.
- The breakdown updates automatically and includes:
- Exact Age — years, months, and days lived
- Total Months / Weeks / Days — the same age expressed as a single running total
- Born on a — the day of the week the date of birth fell on
- Next Birthday and Days Until Next Birthday — a countdown to the next anniversary, or "Today!" if it falls on the "as of" date
- Turning — the age that birthday will mark
Results can be copied or downloaded as a CSV file.
FAQ
How is age calculated exactly?
The calculator counts whole years, then whole months, then whole days between the two dates — the same way you'd count on a calendar. For example, someone born June 15, 1990 is 33 years, 8 months, and 15 days old on March 1, 2024: the 34th birthday hasn't happened yet, so the year count stays at 33, and the remaining 8 months and 15 days are counted from the last birthday (June 15, 2023) up to March 1, 2024.
What about leap year birthdays (February 29)?
People born on February 29 only have a "real" birthday once every four years. In non-leap years, the calculator treats March 1 as the observed anniversary — both for counting a completed year of age and for the "next birthday" countdown. So a February 29 birth date measured on March 1 of a non-leap year shows as exactly turning that year's age, with the countdown at zero.
Why does "Total Days" not simply match years × 365?
Because real years aren't a fixed length — leap years add a day roughly every four years. Total Days is computed as the exact number of calendar days between the two dates, which is what makes it consistent with the years/months/days breakdown above it.
Can I calculate age as of a past or future date, not just today?
Yes — set the "As of Date" field to any date to see the age (and next-birthday countdown) as of that date, whether it's in the past or the future. Leaving it blank always uses today's date.
Is my data sent anywhere?
No. Both dates are processed entirely in your browser — nothing is uploaded or stored, and the calculation works the same way offline.