Age Calculator
Work out an exact age in years, months and days from a date of birth, plus total days and the countdown to the next birthday. Runs in your browser.
Runs entirely in your browser — nothing is uploaded
Not always today — forms often ask for an age on a particular date.
Fill in both dates.
The second date is editable on purpose
Most age calculators assume you mean today. Forms very often do not: they ask for an age as it will be on the first day of a school year, on the date of a flight, on the day a policy starts, or on a closing date for applications.
So the reference date is a field rather than a fixed value, with a button for the common case.
How 29 February is handled
A birthday on 29 February has no date at all in three years out of four. Something has to be chosen, and this tool counts it as falling on 1 March in a common year.
That is the rule most jurisdictions use for coming of age, and it is the more defensible option: 28 February would place the birthday a day before the actual anniversary of the birth rather than after it. The tool says which rule it applied when it matters, rather than leaving you to work out why a number looks a day out.
Why the total months figure looks odd
Because a month is not a fixed number of days, so no two of these figures can be derived from each other. The years and months are counted as whole calendar steps — the way anybody would describe an age out loud — and the leftover days measured from that point.
The total days figure is given separately for anything that needs a plain number, such as a form asking for age in days or a medical calculation that cannot use approximate months.
A date of birth is not a small thing to hand over
It is one of the more identifying facts about a person, and it appears in the security questions of a great many institutions. Typing one into a website that sends it to a server, for arithmetic a browser can do without help, is a poor trade.
Here it is typed into this tab, used for the sum, and gone when the page closes. Nothing is transmitted, nothing is stored, and there is no account to create. The page keeps working offline, which is a reasonable way to check the claim.
Frequently asked questions
Can I work out an age on a date other than today?
Yes, and it is the reason the second date is editable rather than fixed. Forms routinely ask for an age as it will be on a particular day — the start of a school year, the date of a flight, the day a policy begins — and that is rarely today.
How is a 29 February birthday handled?
In a common year the birthday is treated as falling on 1 March. That matches the rule most jurisdictions use for coming of age, and it is the more defensible of the two options: 28 February would put the birthday a day before the actual anniversary rather than after it.
Why does the age in months not equal the years times twelve plus something obvious?
Because calendar months vary in length, so a month is not a fixed number of days. The years and months are counted as whole calendar steps and the leftover days measured from there — which is how people describe an age, and why the total days figure is given separately for anything that needs a plain number.
Is the date of birth stored or sent anywhere?
No. It is typed into this tab, used for the sum and forgotten when the page closes. Nothing is transmitted, nothing is saved, and there is no account. A date of birth is one of the more identifying things about a person, which is a good reason not to hand it to a server for arithmetic a browser can do.
What is the countdown to the next birthday counting?
Whole days from the reference date to the next occurrence of the birthday. On the birthday itself it reads zero rather than jumping to a year away, because that is the answer somebody asking on the day actually wants.