Calculate exact age from date of birth
An age calculator finds the exact time between a date of birth and any other date, broken down into years, months, and days. It's used for everything from checking eligibility for school, retirement, or legal milestones to simply settling an argument about how old someone really is.
This calculator counts whole years first, then whole months, then leftover days. When the end date's day of the month is earlier than the birth day, it borrows the length of the month before the end date. That is why someone born on 29 February is shown as turning a year older on 1 March in a non-leap year.
Age = Current Date − Date of Birth, carried into full years, then remaining months, then remaining days
| Calculation | Expression | Result |
|---|---|---|
| Leap-day birthday on 1 March | born 29 Feb 2000, on 1 Mar 2025 | 25 years, 0 months, 0 days |
| The day before | born 29 Feb 2000, on 28 Feb 2025 | 24 years, 11 months, 30 days |
| Total days lived | 29 Feb 2000 to 1 Mar 2025 | 9,132 days |
Subtract your birth year from the current year to get an estimate, then adjust: if today's month/day is before your birth month/day, subtract 1 year, then count the remaining months and days separately. An age calculator does this automatically and avoids off-by-one errors around birthdays.
Differences usually come from how leap years and month lengths are handled, or whether the calculator counts the birth date itself as day zero or day one. A reliable calculator always counts a full year as only complete once the birthday date has passed.
Chronological age is simply the time elapsed since birth. Legal age refers to age thresholds set by law or policy — such as 18 for voting, 21 for drinking in the US, or a specific birthdate cutoff for school enrollment or retirement benefits — which may use different rounding rules than a simple age calculation.
Leap years add an extra day (February 29) roughly every 4 years. This doesn't change how many full years old someone is, but it does affect exact day counts — for example, someone born on February 29 has a true birthday only once every 4 years.
Yes — enter any end date instead of today's date to find someone's age on a specific past or future date, which is useful for verifying age eligibility on a contract signing date, exam date, or historical event.
It follows its borrow rule rather than a legal rule. For someone born on 29 February 2000, 28 February 2025 shows 24 years, 11 months and 30 days, and 1 March 2025 shows 25 years exactly. Check local law if a legal cutoff depends on the birthday.