Age Calculator
Enter a date of birth and get the exact age in years, months and days. The second field is set to today, but you can move it to any date to answer "how old will she be at the wedding" or "how old was he when the photo was taken".
Defaults to today. Move it forwards or backwards to get the age at any moment.
How the years, months and days are worked out
Age is not a division. You cannot take the days someone has lived, divide by 365.25 and expect the months and days to come out right, because months are between 28 and 31 days long and the answer depends on which ones the person lived through.
This calculator counts whole months from the birth date first, then the leftover days from that anniversary. Adding a month clamps to the end of the month where it has to: one month after 31 January is 28 February, because 31 February is not a date. The remaining days are counted from there.
That convention is why two age calculators can disagree by a day. Some subtract the day numbers and borrow from the previous month, which gives a different remainder for births on the 29th, 30th and 31st. The years figure is the same in both — it is only the months-and-days tail that moves. If you need a number nobody can dispute, use the total days lived.
Born on 29 February
A leap-day birthday only has a real anniversary every four years, so every calculator has to pick a rule. This one clamps to 28 February: someone born on 29 February 2024 is treated as turning one on 28 February 2025.
That is a choice, not a fact. Plenty of calculators use 1 March on the grounds that a full year has not elapsed until the day after 28 February. Legal systems differ too, and the rule that applies to a driving licence or a pension in your country may not be the rule used here. If the exact day matters legally, check the rule where you are rather than trusting any calculator, including this one.
Age is a calendar fact, not a clock fact
This tool works on whole calendar dates. It does not ask for the time of birth, and it treats every date as the same date everywhere in the world.
That is almost always what you want, and it hides a genuine ambiguity. A baby born at 23:40 in Auckland was born on a date that was still yesterday in London. Passports record the local date of the place of birth, so that is the date to enter here. If you want an age accurate to the hour rather than the day, this is the wrong tool — the time of day is not part of the calculation at all.
Where the answer can still be the wrong number
The arithmetic here gives your international age: the number of complete years since you were born. Several systems in daily use do not.
- Insurance. Life insurers often price on "age nearest birthday", which rounds you up for half the year. Being told you are 41 when you are 40 years and 7 months is not an error in their system.
- East Asian age reckoning. The traditional Korean count gave you age one at birth and added a year every New Year, making you up to two years older than the international figure. South Korea moved official and administrative age to the international count in June 2023, but the traditional number still turns up in conversation.
- School years and cut-off dates. Eligibility is usually "age on a fixed date", not age today, which is why the second field above exists. Set it to the cut-off date and read the answer there.
Two further limits worth knowing. Dates are handled in the proleptic Gregorian calendar, so births recorded before a country switched from the Julian calendar — Britain in 1752, Russia in 1918 — will not line up with the historical record. And the "days lived" figure counts calendar days, not elapsed 24-hour periods, so it does not care that two of those days were 23 and 25 hours long wherever clocks change.
Frequently asked questions
How is exact age calculated?
Whole years first, then whole months from the last birthday, then the leftover days. The tool counts complete units only, so you are 40 until the moment your 41st birthday arrives, no matter how close it is.
What about people born on 29 February?
This calculator clamps the anniversary to 28 February in ordinary years, so a leap-day baby ages on 28 February. Other calculators use 1 March, and the legal rule varies by country. For anything official, check your local rule.
Why does another age calculator show different months and days?
Because there is no single correct way to split a duration into months and days when months differ in length. The years always match. The disagreement is in the tail, and it only appears for births late in a month.
Does the time of birth matter?
Not here. The calculation works on calendar dates, so a birth at 00:10 and one at 23:50 on the same day give the same age. If you need an age to the hour, this tool will not give it to you.
Can I work out someone’s age on a past or future date?
Yes — that is what the second date field is for. Set it to the day of the exam, the wedding or the photograph, and the age is calculated as of that date instead of today.
Last updated September 19, 2026