Age Calculator at a glance
- What it does
- Calculate an exact age or the duration between two dates in years, months, days, weeks and hours, with leap years handled correctly.
- Where it runs
- Entirely in your browser — no data is uploaded
- Works offline
- Yes, once the page has loaded
- Cost
- Free, with no account and no usage limit
- Category
- General Calculators
How to use the age calculator
- Enter the date of birth, or the earlier of two dates.
- Set the end date - today by default, or any date to work out an age at a particular moment.
- Read the breakdown in years, months and days, plus total days and hours.
How age is counted
The convention used almost everywhere is completed years: you are 30 until the day before your 31st birthday. The calculation walks forward year by year, then month by month, then counts remaining days - which is why the day component varies depending on the length of the month you land in.
This matters when an exact figure has legal weight - eligibility thresholds, insurance bands, pension dates. It is also why two calculators occasionally disagree by a day: they differ over whether a month step from 31 January lands on 28 February or 3 March.
Not every culture counts this way. Traditional East Asian age reckoning counted a newborn as one year old and added a year at new year, so a person could be "two" at a few days old. South Korea used this system alongside the international one until standardising in 2023.
Leap years and 29 February
A leap year is divisible by four, except centuries, except centuries divisible by 400. So 1900 was not a leap year and 2000 was. That rule keeps the calendar aligned with the solar year to within a day every three thousand years or so.
People born on 29 February - about one in 1,461 - have a birthday in only one year in four. Legally, jurisdictions differ on whether a non-leap-year birthday falls on 28 February or 1 March, which occasionally matters for a coming-of-age threshold.
The calculation here counts actual elapsed days, so leap days are included automatically wherever they fall in the interval.
What people calculate
- Exact age for a form - visa applications, insurance, medical intake.
- Age at a future date - whether someone will meet an age threshold by a deadline.
- Length of service for leave entitlement, notice periods or long-service recognition.
- Days until an event - a deadline, a wedding, a launch.
- Gestational and paediatric ages, where a difference of days genuinely matters.
- Milestones - your 10,000th day is a little before your 28th birthday.
Edge cases worth knowing
Month arithmetic is ambiguous. One month after 31 January is not a well-defined date. Systems either clamp to the last day of the month or roll over, and the two answers differ.
Time zones can shift the date. A birth recorded at 11pm in one zone is the following day in another. For a precise age, use the local date at the place of birth.
Calendar reform. Dates before the Gregorian changeover need care - Britain and its colonies skipped eleven days in September 1752, and different countries changed in different centuries. Historical dates are often recorded in the old style.
Frequently asked questions
By completed years: you remain a given age until the day before your next birthday. The calculator then counts remaining whole months and days on top.
The total elapsed days are always exact. For the years-months-days breakdown in a non-leap year, the birthday is treated as falling on 28 February, which is the more common legal convention.
Yes - set the end date to whatever you need. Useful for checking whether someone will meet an age requirement by a particular deadline.
Almost always a difference in how month boundaries are handled, or a time zone difference shifting one of the dates. Total elapsed days should agree; the years-months-days breakdown may not.
No. The calculation happens in your browser and nothing is transmitted or saved.
Nothing you enter here leaves your browser
Age Calculator does its work in JavaScript running on your own device. The page loads once, and after that there is no upload step and no server involved — which matters here because your figures are yours, and nobody needs a record of them.
You can verify this rather than taking our word for it: load the page, disconnect from the internet, and the tool keeps working. Our privacy policy sets out what is and is not collected, and this guide explains why the distinction matters.