Free tool
Age calculator
Enter a date of birth and get the exact age in years, months and days — plus totals, the weekday of birth, and how long until the next birthday. You can also measure to any past or future date.
Dates are handled in UTC so the result does not shift when you cross a time zone, and nothing you type is sent to us.
Enter a date of birth to see an exact age.
Why simple age calculations go wrong
Most quick methods divide the number of days between two dates by 365.25 and round. That is fine for a rough figure and wrong in the cases people actually care about — the ones near a birthday, or spanning a leap year, or where a form demands an exact years-months-days breakdown.
The correct method works down the calendar in units. Subtract the day-of-month first; if the result is negative, borrow the true number of days from the previous month — which is 28, 29, 30 or 31 depending on which month it is and whether the year is a leap year. Then subtract months, borrowing twelve if needed, then subtract years. That is what this calculator does, which is why its answer matches what a registrar would write down.
When you need an exact age
- Visa and immigration forms, which often ask for age in years and months at the date of application rather than today.
- Insurance and pension eligibility, where crossing a threshold by a single day changes the band you fall into.
- School and exam entry, which is usually assessed at a fixed cut-off date rather than at enrolment.
- Paediatric and developmental records, where the first years are tracked in months rather than years.
- Legal documents, where “aged 17 years and 11 months” and “aged 18” are entirely different situations.
A note on leap days
People born on 29 February have a birthday that exists roughly once every four years. For everyday purposes the convention in most English-speaking countries is that the birthday falls on 1 March in a common year, and that is what this calculator assumes for the countdown. Legal systems vary — some treat 28 February as the operative date for reaching a statutory age — so where a precise legal date matters, confirm the rule in your own jurisdiction rather than relying on any calculator.