Work out an age
Leave the second date empty to measure to today.
Total time lived
The same span, counted in other units.
Birthday
What day it fell on, and when the next one arrives.
How the calculation works
Age is worked out by counting complete years from the date of birth, then complete months, then the days left over — the same method used on official forms and by most legal definitions. Someone born on 15 May 1990, measured on 14 April 2026, is 35 rather than 36, because the birthday has not yet come round that year.
Calendar realities are handled properly. Month lengths vary, so the leftover days are measured against the actual length of the preceding month rather than an assumed thirty. Leap years are counted as they fall, which keeps long spans accurate — the difference is not trivial, since it accumulates by about a day every four years.
Using the second date
Filling the optional second field changes the question from "how old is this person now" to "how old was, or will be, this person on a particular day". That covers a lot of real paperwork: whether a child meets a school entry cut-off, whether someone reaches a qualifying age by a policy or contract date, what age a person was on a historical date, or how old someone will be at a future event.
Where exact age is required
Visa and immigration paperwork often asks for age in years and months as of a specific processing date. School admissions apply cut-offs on a fixed day of the year. Medical dosing for young children is frequently calculated by age in months. Sports and competition categories draw hard lines by birth date. Pension, benefit and insurance eligibility all turn on precise thresholds. In every one of those, being a month out matters.
A note on counting age
The method used here — age starting at zero and rising on each birthday — is the most widely used system internationally, but it is not universal. Some East Asian traditions have historically counted a newborn as one year old, with age rising at the new year rather than on the birthday, which can put a person one or two years older than the international reckoning. If you are filling in an official form, the system used here is almost always the one expected.
Frequently asked questions
Does this handle leap years?
Yes. The calculation works from real calendar dates, so 29 February is counted whenever it falls inside the span.
What about someone born on 29 February?
The tool measures from the actual date, so the totals stay exact. Which day counts as the birthday in non-leap years varies by country; most treat 1 March as the operative date for legal purposes.
Can I calculate age at a future date?
Yes. Put the future date in the second field to see what the age will be that day.
Is my date of birth stored?
No. The calculation runs in your browser and nothing is transmitted or saved.
I want the gap between two events, not an age.
Use the date difference calculator, which is built for durations between any two dates and can count working days.