Age Calculator

Exact age in years, months and days, plus a breakdown of every unit of time.

Date of birth

Age at the date of

Pick a date of birth above to see your age.

How to use

Enter your date of birth (or any past date).
Optionally change the target date - it defaults to today.
See your exact age in years, months, days, plus totals in every unit.
The card also shows the weekday you were born and your next birthday.
Hit Copy summary to paste the result into a message or note.

Frequently asked questions

How is the age in years, months and days calculated?

Months have different lengths, so the calculator computes complete months and then counts remaining days based on the actual calendar, matching how most people informally express age.

Does it handle leap years?

Yes. The calendar arithmetic accounts for leap years, so a birthday on 29 February correctly identifies the next valid birthday in non-leap years.

Can I use it for any two dates?

Yes. Set both the start date and target date manually to find the difference between any two moments, such as time since a hire date or anniversary.

Is my birthday data sent anywhere?

No. The page processes the date entirely in your browser; nothing about you or the date you typed is transmitted.

Why exact age is trickier than subtraction

Subtracting years works until months and days disagree. Someone born 15 March 1990 is not yet 36 on 12 June 2025... they are 35 years, 2 months and 28 days. Correct age math borrows days from the previous month's actual length and months from the year, which is why February and leap years complicate hand calculation. A person born 29 February has a calendar birthday only every four years, though legally most jurisdictions treat 1 March (or 28 February, depending on the country) as the milestone date in off years.

Ages the calendar cares about

Days are the unit for infants (vaccination schedules run on exact days and weeks), months up to age two, then years.
Pension, insurance and visa rules often hinge on age at a specific future date, not age today. Compute "age on 1 September 2027", not "age now".
School cutoffs compare birth date against a fixed enrolment date, so two children born nine days apart can land a full school year apart.

Fun with the same arithmetic

The same engine answers less bureaucratic questions: your 10,000th day alive lands about 5 weeks after your 27th birthday; a billion seconds is roughly 31.7 years; and "how many days until I turn 40" is just the calculation run forward. Day-precision age is also how you settle which of two people born the same year is actually older, a dispute the tool resolves in seconds.

Date arithmetic beyond birthdays

The same engine that computes age answers any two-date question: days until a deadline, the exact length of an employment period for a CV, how long a warranty has left, or the duration between two historical events. Two conventions decide the answer at the edges: whether both endpoints count (an event from the 1st to the 3rd spans two days or three depending on inclusivity), and what a "month" means when the start date is the 31st and the next month has 30 days. Institutions resolve these differently, which is why two correct calculators can disagree by a day... and why, for anything contractual, the convention deserves a sentence in writing.