Age Calculator (exact years, months, days)
Work out an exact age in years, months, and days from a birth date, plus total days, weeks, and months lived and the next birthday.
Working out an exact age
Age is the calendar difference between a birth date and a reference date, expressed in whole years, then leftover months, then leftover days. It sounds simple, but doing it correctly means respecting month lengths and leap years rather than dividing by 365.
Why dividing by 365 goes wrong
Approximating an age as days ÷ 365 drifts by roughly a day per four years, because of leap days. Over a lifetime that's a fortnight or more of error. The right approach is calendar arithmetic: count the years first, then the months, then borrow days from the preceding month when the day-of-month hasn't been reached yet — which is exactly what this calculator does.
The 29 February question
People born on a leap day have no birthday in most years. Conventions differ — some jurisdictions treat 28 February as the legal birthday in common years, others 1 March. This calculator counts the next actual 29 February, so a leap-day birthday shows a longer wait in non-leap years. That's the literal answer, not necessarily the legal one where you live.
Worked example
Someone born on 15 June 1990, evaluated on 15 March 2024, is 33 years, 9 months and 0 days old — around 12 327 days, or about 1761 weeks. Their next birthday falls on 15 June 2024, roughly three months away. Change the "as of" date to work out an age at any past or future point.
Related
For a general gap between two dates rather than an age, use thedate difference calculator.