Age Calculator

Your age is the exact time elapsed to the chosen date, accounting for leap years and varying month lengths — not just a subtraction of years. Handy for precise milestones and eligibility dates.

Why this one is different

Three rows, no decimals: the age as whole years, months and days, the total days lived as one running count, and how long is left until the next birthday. A birth date later than the comparison date is refused with a message rather than handed back as a negative age, which is what happens when the two boxes get filled in the wrong order.

Time, precisely counted

The leap-year quirk that trips up simple age maths

Working out age looks trivial until February 29th, months of different lengths and leap years get involved. Subtracting years alone quietly drifts by days — which matters for legal ages, milestones and pension dates.

This calculator borrows across months the way a real calendar does, so your age in years, months and days is exact — right down to the countdown to your next birthday.

How it works

The calculator counts complete years, then complete months, then the remaining days between your date of birth and the chosen date. It borrows correctly across months of different lengths — including leap years — so a birthday on the 31st is handled the same way calendars do.

Example calculation

Born 14 March 1990, measured on 18 July 2026:

Age = 36 years, 4 months, 4 days
Total days ≈ 13,275

What an exact age is actually used for

For most conversations an age in whole years is enough. The places it is not are all administrative: school year eligibility, which in England is set by whether a child turns five before 1 September; pension and state benefit dates, which key off an exact date rather than a birthday; insurance quotes, which frequently price on age next birthday rather than age today; and medical dosing for infants, which is measured in completed weeks or months from birth.

That last case is why the calculator reports years, months and days rather than a single figure. A paediatric chart plots a child at, say, 14 months and 3 days, not at 1.2 years, and rounding a baby's age to the nearest year loses the entire signal.

The 29 February question comes up every four years. Legally, in most jurisdictions including the UK, a person born on a leap day is treated as having their birthday on 1 March in a common year for the purpose of reaching a given age. That is the convention used here. It is worth knowing that the alternative convention — 28 February — exists in some countries and in some contracts, so if a single day matters to something you are relying on, check the wording rather than the calculator.

Frequently asked questions

Can I calculate age at a future date?＋

Yes — set the second date to any date, past or future, to see how old you were or will be then.

Are leap years handled?＋

Yes. Day counting uses the real calendar, so 29 February and leap years are counted accurately.

How is age counted in months and days?＋

Whole years are counted first, then whole months from the last birthday, then remaining days. This matches the everyday convention of saying someone is 34 years and 5 months old.

What happens with a 29 February birthday?＋

In non-leap years the birthday is treated as 1 March for age purposes in most jurisdictions, which is the convention used here. Legal definitions occasionally differ.

Why does my age in days seem high?＋

A year averages 365.25 days, so each decade adds over 3,650 days. Someone at 40 has lived roughly 14,600 days, which surprises most people the first time they see it.

Can I work out an age gap between two people?＋

Yes, by calculating each age at the same reference date and subtracting, or by using the date difference calculator on the two birth dates directly.

Formula

Age = today − date of birth

The result is broken into whole years, then the remaining months, then the remaining days, counting real calendar months (not fixed 30-day months) so it matches how ages are stated in everyday life.