Age Calculator

Exact age in years, months and days — plus days until the next birthday.

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About this calculator

Exact age matters more often than you'd think: forms, eligibility thresholds, pensions, school entry, insurance quotes. This calculator gives age in years, months and days at any date — not just today — plus the total days lived and a countdown to the next birthday.

The formula

Age = calendar difference between date of birth and the chosen date

Worked example

Born 15 May 1985, on 18 July 2026 you are 41 years, 2 months, 3 days — 15,039 days.

Common mistakes

Computing age as year − year, which is wrong before the birthday each year.
Using days ÷ 365.25 and getting month boundaries wrong for official forms.
Forgetting that some eligibility rules use age at a specific date (e.g. 1 September for school entry).

Frequently asked questions

The calculator uses real calendar arithmetic; in non-leap years the next-birthday countdown lands on 1 March, matching common legal practice.

Yes — set the "age at" date to anything, e.g. a policy start date or exam date.

A year is 52 weeks and a bit — the weeks figure is total days ÷ 7, the exact value.

Assumptions & limitations

Gregorian calendar throughout.

Sources & verification

This calculator applies the standard formula published above to the figures you enter — it relies on no external statutory data. The formula and the worked example were checked by hand against each other.

Formula last verified: 24 July 2026

Maintained by: Steve Davis, Founder & Editor — see our editorial standards

Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).