Age Calculator
Enter a date of birth to get an exact age using calendar arithmetic — not an approximation based on dividing by 365.25.
| Day of the week born | — |
| Next birthday | — |
| Days until then | — |
| Leap days lived through | — |
How to use the Age Calculator
- Pick the date of birth.
- Leave the second date as today, or change it to work out an age at any other point in time.
- Press Calculate age to see the exact years, months and days, plus totals and the next birthday.
How exact age is calculated
Age is calendar arithmetic, not division. The method here is the same one used on official forms: subtract the years, then the months, then the days, and borrow when a component goes negative.
Borrowing is where implementations differ. If someone born on 31 January is having their age taken on 1 March, the day count borrows from February — which has 28 or 29 days depending on the year. This tool borrows the length of the month before the end date, which is the convention that keeps ages consistent as time passes.
Dividing total days by 365.25 is the shortcut to avoid. It drifts by several days over a lifetime and can report someone as a year older the day before their birthday.
Birthdays on 29 February
People born on a leap day have a birthday that exists once every four years. Jurisdictions handle it differently — some treat 28 February as the legal birthday in common years, others use 1 March. There is no universal rule.
This tool takes the arithmetic route: it uses the actual date and lets the day component carry the difference. The "next birthday" row shows the nearest real 29 February. If you need a legal answer for a document, check the rule where you live.
Frequently asked questions
Why does it not match the age my government form shows?
Some official systems count age in completed years only, ignoring months and days. Others use a "reckoning" convention that adds a year at the New Year. The whole-year figure here matches the completed-years method used almost everywhere.
Can I calculate age for a past or future date?
Yes. Change the second date to anything you like — a job start date, a policy renewal, a date decades ahead. The calculation is the same.
Does it handle time zones?
Dates are treated as calendar dates without a time component, which is how birthdays work. Someone born late at night in one zone has the same birthday everywhere.
Is my date of birth stored anywhere?
No. The calculation runs in your browser and nothing is sent, saved or logged.
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