Age CalculatorPrivate, Instant, In Your Browser
Enter a date of birth and we'll break the age down precisely — full years, remaining months and leftover days — and count down to the next birthday. Calendar months have different lengths, so "how old exactly?" is fiddlier than it looks; the calculator walks the real calendar instead of dividing by 365. Like every tool we build, it runs entirely on your device: your date of birth stays in this tab.
Updated January 2026
Pick a date of birth to see the exact age.
Calculated on your device — your date of birth is never sent anywhere.
About this tool
Chronological age is elapsed time since birth measured against the Gregorian calendar — the civil calendar introduced in 1582, whose uneven months and leap rules make exact age math trickier than dividing by 365.
- The Gregorian calendar was introduced by Pope Gregory XIII in October 1582 to correct the Julian calendar's drift against the solar year.
- Its leap rule — every 4th year, except centuries not divisible by 400 — makes the average year 365.2425 days; 2000 was a leap year, but 1900 wasn't and 2100 won't be.
- Because months run 28-31 days, an exact age in years, months and days can only be computed by walking the actual calendar, not by dividing a day count.
About the Age Calculator
"How old, exactly?" is a calendar-walking problem, not a division problem. Months run 28 to 31 days, leap years add a day roughly every fourth February, and "n years, m months, d days" only comes out right if you step through the actual Gregorian calendar — which this calculator does, rather than dividing a day count by 365.25 and rounding the error under the rug.
The exact figure matters more often than trivia: eligibility cutoffs (school enrollment, pension ages, visa and competition age limits) are defined to the day; legal and medical paperwork asks for age at a specific past date; HR systems compute service durations the same calendar-walking way. The calculator gives years, months and days, plus a live countdown to the next birthday — and February 29 birthdays are handled with the common civil convention (February 28 in non-leap years).
It also works backwards and sideways: enter any date of birth to check a relative's age for a form, an age on a document, or how old someone was on a given date in history — the arithmetic is always relative to your device's current date.
A date of birth is a key piece of identifying information — one of the standard "verify your identity" fields — so it's worth noting the whole calculation is a few lines of JavaScript running in your tab. Nothing you type is transmitted, logged or stored anywhere.
Frequently Asked Questions
How is exact age calculated?
We count full years first, then full calendar months since the last birthday, then the days left over. Because months are 28–31 days long, this walk through the real calendar is the only way to get an exact answer — dividing total days by 365.25 gives only an approximation.
What happens if I was born on February 29?
In non-leap years the calculator treats February 28 as the birthday anniversary, which is the most common civil-law convention. Your next-birthday countdown targets the next date that actually exists.
Is my date of birth uploaded or stored?
No. The whole calculation is a few lines of JavaScript running in your browser tab. Nothing is transmitted, logged or stored — close the tab and the date is gone.
Can I calculate someone else's age, or an age at a past date?
Any date of birth works, so you can check the age of a relative, a document or a historical figure. The result is always relative to today's date on your device.
Every conversion runs 100% in your browser — zero files uploaded, ever.
How to verify it yourself →