Free online tool
Age Calculator
Enter a date of birth to see the exact age in multiple units.
Calculating age the right way
Age is usually stated in years, but there are many reasons to know it more precisely — legal documents, medical records, milestone birthdays, or just curiosity. This calculator gives you an exact figure in years, months and days, plus totals in weeks, hours and minutes.
How it works
Given a date of birth and a target date, the tool counts complete years first, then remaining months, then remaining days. It correctly handles month-length differences and leap years using standard calendar math.
Uses beyond birthdays
You can also use it to work out how long ago an event happened — a job start date, a project kickoff, an anniversary, or the age of a pet.
+Does it handle leap years?
Yes. The calculation uses real calendar dates, so February 29 and leap years are respected.
+Is my birth date stored?
No. Everything runs in your browser.
Counting years, months and days between two real dates
Age math sounds trivial until you hit February 29th, a month with fewer days than the one you started in, or a birthday that falls on a leap day in a non-leap year — this calculator handles those edge cases so you don't have to count on your fingers.
Because the Gregorian calendar has irregular month lengths and an occasional extra day, even careful manual arithmetic tends to be off by a day here or there.
Why simple subtraction fails
You can't just subtract year, month and day components independently, because months have different lengths. Someone born on 31 January turning a month older on 28 February (or 29th in a leap year) needs the day component borrowed from the previous month, exactly like carrying in subtraction. The calculator resolves this by walking calendar months rather than assuming a fixed 30-day month.
The leap-day birthday problem
Someone born on 29 February 2000 legally turns a year older on 28 February or 1 March in non-leap years, depending on the convention used; most systems, including this one, treat the anniversary as falling on 28 February so the age increments consistently every calendar year instead of only once every four.
Worked example
Born 15 March 2000, today 10 June 2024: that's 24 years, 2 months and 26 days old, and 24 years old in the everyday sense since the March birthday has already passed this year. Total elapsed days work out to roughly 8,853, factoring in six leap years (2000, 2004, 2008, 2012, 2016, 2020, 2024) along the way.
Why total days matter beyond curiosity
Some contexts care about age in raw days rather than years — infant medical charts track age in days or weeks for the first several months, some legal age thresholds ('at least 18 years and 1 day') hinge on the exact date rather than the calendar year, and pregnancy due-date calculations count gestational days precisely. In all of these, an off-by-one from ignoring a leap year can genuinely matter.
Different cultures count age differently
Western age counting starts at zero at birth and increments on each birthday. Traditional Korean age, by contrast, counted a newborn as already one year old, with everyone aging up together on New Year's Day rather than on individual birthdays — a system officially phased out in 2023 in favor of the international standard, but still occasionally referenced informally.
Milestone ages and legal thresholds
Many legal and contractual thresholds hinge on turning a specific age on a specific date — voting eligibility, drinking age, retirement benefit eligibility, and insurance rate tiers all change at an exact birthday, not an approximate one. Getting the date arithmetic even one day wrong can matter in these contexts far more than it would for a casual 'how old am I' question, which is part of why this calculator resolves the leap-day and month-length edge cases precisely rather than approximately.
People also search for
- age calculator by date of birth
- how many years months days old am i
- calculate age between two dates
- exact age calculator
- days since birthday calculator
- leap year birthday calculator
- age in days calculator