Age Calculator

How this is calculated

Complete years first, then complete months, then the remaining days — walking the actual calendar so month lengths and leap years are always right. Example: born 15 June 1990, on 20 May 2026 you are 35 years, 11 months, 5 days old — 13,123 days in total. The "next birthday" line counts down to the day your years number ticks over.

Why "years, months and days" is harder than a day count

Counting days between two dates is unambiguous. Expressing the same span as years, months and days is not, because months have different lengths and the answer depends on the order you subtract in. The standard approach — the one used on birth certificates, visa forms and this page — counts complete years first, then complete months from the last birthday, then the remaining days. That ordering matters: doing it the other way round can produce a different month count for the same two dates.

This is why two age calculators can disagree by a day or two and both be defensible. If a form specifies a method, follow the form. If it does not, the convention above is the one almost every official system uses.

The 29 February problem

Someone born on 29 February has a birthday that exists in one year out of four. Law resolves this differently in different places: in England and Wales a person born on 29 February legally turns 18 on 1 March in a non-leap year, whereas some jurisdictions treat 28 February as the anniversary. Neither is wrong; they are different conventions, and no calculator can pick for you.

The same ambiguity affects month arithmetic generally. One month after 31 January is either 28 February or 3 March depending on whether you clamp to the end of the month or overflow into the next. This page clamps, because that is what people mean when they say "a month later", and it is what most date libraries do — but it means adding a month and then subtracting one does not always return you to the original date.

Age reckoning is not universal

The system where a newborn is zero and gains a year on each birthday is the international standard, but it is not the only one that has been in use. The traditional East Asian system counted a baby as one at birth and added a year at the new year, so a child born in December could be "two" a few weeks later. South Korea formally moved to international age reckoning in 2023, having used all three systems simultaneously for different purposes. If you are cross-checking an age against a historical or foreign document, this is a real source of one- and two-year discrepancies.

Where exact ages actually matter

Precise age drives more thresholds than people notice: school entry cut-offs, which frequently hinge on whether a birthday falls before a specific date; eligibility for licences, contracts and pensions; insurance pricing bands; and paediatric drug dosing, where "two years" and "23 months" can mean different guidance. In each case the rule is defined against a date rather than an approximate age, which is why "he's nearly three" is not an answer a form will accept.

For anything with legal weight, use the raw date and the rule as written rather than a rounded age. This calculator gives you the exact figures; the threshold rules belong to whoever is asking.