Free age calculator
Enter your date of birth and this age calculator tells you exactly how old you are — your age in years, months, and days plus your total days alive, with month lengths and leap years handled automatically. The count runs to today and is updated live, as you type.
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Age calculated from date of birth to today.
Results are estimates. Consult a professional.
How old am I? Your exact age in years, months, and days
This age calculator answers "how old am I?" precisely. Enter your date of birth and it returns your exact age in years, months, and days — for example 35 years, 8 months, and 17 days — plus the total number of days you have been alive. The count runs to today's date and updates the moment you change the birth date.
Working out an age in your head is harder than it looks, because months are different lengths and leap years add a day every four years. A calculator does the calendar arithmetic for you, so the result is accurate whether you were born last year or eighty years ago. The same maths gives your chronological age — the standard measure used on school enrolment forms, psychological tests, and legal age checks.
How age is counted (the subtract-then-borrow rule)
Age is not one big division — it is three separate calendar counts: full years, then the leftover full months, then the leftover days. The calculator subtracts the parts of each date and "borrows" when a part comes out negative, exactly the way you borrow in column subtraction.
- Subtract the years: reference year − birth year.
- Subtract the months: reference month − birth month.
- Subtract the days: reference day − birth day.
- Borrow days if needed: if the day count is negative, drop one month and add the number of days in the previous calendar month.
- Borrow months if needed: if the month count is then negative, drop one year and add 12 months.
Your age in completed years only ticks up on your birthday. Someone who has lived 3 years and 11 months is still 3 years old; they turn 4 the day the calendar reaches their birth date again. That birthday-boundary rule is the standard Western reckoning the calculator uses.
A worked example: how the age calculator counts
Daniel was born on 15 September 1990 and wants his exact age on 1 June 2026. Here is how the calculator works through the subtract-then-borrow rule. (The live tool counts to today's date instead of this fixed date, but the method is identical.)
Step 1 — Subtract each part of the date
Years: 2026 − 1990 = 36. Months: June (06) − September (09) = −3. Days: 1 − 15 = −14. Both the day and month counts are negative, so they need borrowing.
Step 2 — Borrow days from the previous month
Because the day count is negative, drop one month and add the length of the previous calendar month. The month before June 2026 is May, which has 31 days: −14 + 31 = 17 days. The month count is now −3 − 1 = −4.
Step 3 — Borrow months from the year
The month count is still negative, so drop one year and add 12 months: 36 − 1 = 35 years, and −4 + 12 = 8 months.
Step 4 — Read the result
Daniel is 35 years, 8 months, and 17 days old. Counted straight through the calendar, that span is 13,043 days in total — the figure the calculator also shows, with every leap day in those 35 years already included.
Month lengths and leap years
Two things make age arithmetic tricky: months are not the same length, and leap years add a 29th of February every four years. The calculator handles both by working with real calendar dates, not by assuming a fixed "month = 30 days" or "year = 365 days."
| Month | Days | Month | Days |
|---|---|---|---|
| January | 31 | July | 31 |
| February | 28 (29 in a leap year) | August | 31 |
| March | 31 | September | 30 |
| April | 30 | October | 31 |
| May | 31 | November | 30 |
| June | 30 | December | 31 |
When the calculator borrows days, it adds the real length of the previous month from this table — including 29 days for February in a leap year.
Leap years matter most in the total-days figure. A leap year is any year divisible by 4, except century years not divisible by 400 (so 2000 was a leap year, 1900 was not). Over a 35-year span there are roughly eight or nine leap days, and the total-days count picks up each one automatically because it measures the actual calendar distance between the two dates. To check whether a particular year has a 29 February, use the leap year calculator.
Total days alive, weeks, and months
Alongside years-months-days, the calculator reports the total number of days you have been alive — 13,043 in the worked example. That single number is the cleanest way to compare ages or count down to a milestone, because it sidesteps the uneven lengths of months entirely.
- Total days is the exact calendar distance from your birth date to today, every leap day included.
- Weeks are total days ÷ 7 — so 13,043 days is about 1,863 weeks.
- Months as a single number are approximate, because months vary from 28 to 31 days; the years-months-days breakdown is the precise version.
If you only want the running day count, the days alive calculator shows it on its own. To compare two people's ages or find the gap between any two dates, the age difference calculator uses the very same subtract-then-borrow method.
Born on 29 February, and other edge cases
People born on 29 February still age one year every year. In common years there is no 29 February, so the calculator measures the span to 1 March (or 28 February, depending on the convention) — but your completed-years age increases on schedule, the same as everyone else. Only the exact-date celebration is intermittent.
- Birthday today: if the reference date is your birthday, the day and month counts are zero — you are an exact number of years old.
- Born on the 31st: when the previous month is shorter (say, borrowing into February), the calculator uses that shorter month's real length, so the day count stays accurate.
- Future or same-day dates: a birth date in the future has no meaningful age; the tool is built to measure birth date up to the present.
Common age questions
How do I calculate my exact age?
Subtract your birth year, month, and day from today's year, month, and day. If the days come out negative, borrow the length of the previous month; if the months then come out negative, borrow 12 months from the years. The result is your exact age in years, months, and days — which is what this calculator does instantly.
Does the age calculator account for leap years?
Yes. It works with real calendar dates, so every 29 February between your birth date and today is counted automatically — both in the years-months-days breakdown and in the total-days figure.
When does my age go up by a year?
On your birthday. In the standard Western system your completed-years age increases the day the calendar reaches your birth month and day again — not at the start of the year you are turning. Someone who is 3 years and 11 months is still counted as 3.
How this calculator works and sources
This age calculator measures the calendar distance from your date of birth to today using the standard subtract-then-borrow method, borrowing the real length of the previous calendar month so that varying month lengths and leap years are handled exactly. The arithmetic runs entirely in your browser — your birth date is never sent anywhere — and the total-days figure is the precise calendar count between the two dates.
Calculator.net — Age Calculator: exact age in years, months, weeks, and days.Omni Calculator — Age in Years, Months, and Days: the years/months/days method and its handling of unequal month lengths.United States Naval Observatory (USNO) — Leap Years and the Gregorian calendar rule used in the total-days count.Frequently asked questions about the free age calculator
About this age calculator
This age calculator runs entirely in your browser. It measures the calendar distance from your date of birth to today using the standard subtract-then-borrow method — borrowing the real length of the previous calendar month — so varying month lengths and leap years are handled exactly. Your birth date is never uploaded or stored anywhere.
It is one of our free everyday tools — browse the rest on the everyday calculators shelf or see every tool in the full calculator directory. Related tools include the age difference calculator, the days alive calculator, and the leap year calculator.