Age Calculator

Enter a birth date and instantly see the exact age in every unit, when the next birthday lands, and which life milestones are coming up.

When were you born?

Works for any person or thing — people, pets, companies, anniversaries.

Your exact age

—

—total months
—total weeks
—total days
—total hours
—total minutes
—seconds

Next birthday 🎂

—

—days to go
Born on a—
Half-birthday—
Next milestone—

Life milestones

Big round numbers worth celebrating — dates are computed from the birth date above.

Milestone Date Status
Enter a birth date to see milestones.

How this age calculator works

Age sounds simple until you try to compute it. This calculator uses the convention most of the world (and every official form) uses: your age in years goes up on your birthday, and the leftover time is expressed in months and days. Under the hood it subtracts the birth date from the target date with calendar-exact arithmetic — leap years, 28/29/30/31-day months and all — so the result matches what a passport office or school registrar would compute.

Why months and days can be counted two ways

Calendars have uneven months, which creates genuine ambiguity at month edges. Count from 28 February to 31 March: if "one month" means 28 Feb → 28 Mar, the answer is 1 month 3 days. If you treat both dates as "end of month", the answer is exactly 1 month. Both are defensible; this calculator uses the first method — add whole months from the birth day, then count remaining days — because it's the one used by the most popular reference calculators and by most legal age definitions.

Born on 29 February?

Leaplings get a real birthday only in leap years. In common years, this calculator (like JavaScript's own calendar) rolls 29 February forward to 1 March for the "next birthday" countdown. Legally it varies by country: in the UK and Hong Kong a leapling's age changes on 1 March in common years, while in New Zealand and most US states it's 28 February. Either way your years/months/days age here stays calendar-exact.

Not every culture counts age the same way

The system above — you're born at age 0 and gain a year each birthday — is the international standard. But in the traditional East Asian system a baby is born at age 1 and everyone gets a year older together at New Year, so a "Korean age" could run one or even two years ahead of the international one (South Korea officially switched to international age in June 2023). If a grandparent's stated age doesn't match this calculator, that's usually why, not a math error.

Fun with big numbers

Because the calculator also shows your age in total days, hours and seconds, some milestones jump out: you turn 10,000 days old at about 27 years 4 months, hit 1 billion seconds at roughly 31 years 8 months, and reach 20,000 days just before your 55th birthday. The milestone table above computes your personal dates — they make great excuses for a party.

Beyond birthdays

Point the two date fields at anything: how old your dog is in exact days, how long you've been at a job, the precise age of a child in weeks for a pediatric appointment (weeks are the standard for infants under 6 months), or the running age of a company since incorporation. Set the second date into the future to see how old you'll be on a given date — handy for pension and visa forms that ask for "age on" a cutoff date.

Frequently asked questions

How do I calculate my age from my date of birth?
Subtract your birth year from the current year, then subtract one more if your birthday hasn't happened yet this year. For the exact months and days, this calculator adds whole calendar months from your birth day and counts the remaining days — the same method used on official forms.
How many days old am I?
Enter your date of birth and the calculator shows your exact age in total days (plus weeks, hours, minutes and live-ticking seconds). As a rough guide, multiply your age in years by 365.25.
What day of the week was I born?
The calculator shows your birth weekday automatically. It applies the Gregorian calendar rules for any date from 1900 onward, including leap years.
When is my next birthday and how many days away is it?
The next-birthday card shows the date, the weekday it falls on, the age you'll turn, and a live countdown in days. If you were born on 29 February, the countdown uses 1 March in common years.
How does the calculator handle leap years?
All arithmetic is calendar-exact: February has 29 days in leap years (years divisible by 4, except century years not divisible by 400). Total-day counts and year/month/day breakdowns both account for this automatically.
Why does another site give a slightly different months-and-days answer?
Month lengths are uneven, so there are two legitimate ways to count partial months at month edges (for example 28 Feb to 31 Mar). This calculator adds whole months from the birth day first, then counts leftover days — the most common convention.
Can I calculate age at death or age on a past date?
Yes. Set "Age on this date" to any date — a date of death gives a lifespan, a past date gives age at that moment, and a future date shows how old someone will be, which is useful for pension or visa cutoffs.
What is a chronological age calculator?
It's exactly this: age measured by the calendar from birth to a given date. Chronological age is what forms and eligibility rules use, as opposed to "biological age" estimates based on health markers.

Related calculators

Time Date difference Hours Tip Discount