Age Calculator
Last updated: September 23, 2026
Calculate exact age in years, months, days, hours, and minutes.
Pick a date of birth and (optionally) an as-of date. Returns exact age plus the date of the next birthday.
How age is calculated
Enter a date of birth. Optionally enter an as-of date; leave that field blank to use today's date. The main result is a calendar age: completed years, then completed months, then the leftover days. You reach the next year of age on the anniversary of the birth date, not on 1 January. Someone born on 15 March is still the previous age on 10 March.
The month-and-day part borrows when it has to. If the as-of day is earlier in the month than the birth day, the count steps back one month and adds the length of the previous month, including 29 days when that month is a leap February. The same rule produces a clean "0 months, 0 days" on a birthday.
Beside the spoken age, the panel lists total months (years × 12, plus the leftover months), total weeks (full weeks in the day count), and total days between the two dates. Hours are the day count times 24, and minutes are the day count times 1,440. There is no birth time and no clock on the as-of date, so those hour and minute figures expand whole days. A baby born this morning will not show as a few hours old.
Next birthday is the number of days from the as-of date until the next anniversary of the birth date after that as-of date. On the birthday itself, the next one shown is a year ahead.
Worked examples
Example 1: A birthday that has not arrived yet
Born 15 March 2006, as of 10 March 2026. The age is 19 years, 11 months, and 23 days. The 20th birthday is 15 March 2026, which is 5 days after 10 March, so the next-birthday line reads 5 days. Total days lived in that span: 7,300. Full weeks: 1,042, with 6 days left over that the weeks field does not display (1,042 × 7 = 7,294, and 7,300 − 7,294 = 6). Hours: 175,200. Minutes: 10,512,000. Those large numbers are the day count expanded. They are useful on a form that asks "how many days old," and they are not a stopwatch.
Example 2: An exact anniversary
Born 1 January 2000, as of 1 January 2026. The age is 26 years, 0 months, 0 days. The next birthday is 1 January 2027. From 1 January 2026 to 1 January 2027 is 365 days, because 2026 is not a leap year. The years figure does not tick up a day early to "use up" a leap day from an earlier year.
Example 3: A future as-of date
Set the as-of date to a wedding, a race, or the day a form will be signed. The result is the age on that day, which is what most applications want if you will submit them later. Leaving as-of blank always means "the date the browser treats as today," so set the field when the paperwork has its own date.
Example 4: Pets, products, and anniversaries
The arithmetic is the same for a dog born on 1 June 2020 and an as-of date of 1 June 2026: 6 years, 0 months, 0 days. Popular "dog years" charts are a separate story and are not applied here. A product launched on a known date can be aged the same way. For two dates that are not a birth date, and for a business-day count, use the Date Difference Calculator instead.
When to use this
Use it when a form wants age in years, months, and days, when you want the day count behind a birthday, or when you are checking how old someone will be on a future date. Pediatric paperwork often wants the long form for infants. Eligibility dates for voting, a driver's license, or a retirement claim turn on the legal birthday, not on a rounded year. This page performs the calendar math only. It does not decide eligibility.
Retirement math in particular depends on birth year, claiming age, and earnings, not on a day count alone. The Social Security Estimator and the article on claiming at 62, 67, or 70 cover that decision. Come back here only for the age on a specific date.
Common mistakes
- Counting the current calendar year before the birthday. A person born in November is still the prior age through October. The calculator waits for the anniversary.
- Reading hours as clock time. Hours = days × 24. A birth at 11 p.m. and a calculation the next morning are still whole dates.
- February 29 birthdays in a non-leap year. There is no 29 February in 2025, 2026, or 2027. The next-birthday countdown can land on 1 March in those years because the calendar has no 29 February to point at.
- Using age in completed years for a deadline that falls the day before the birthday. Completed years stay put until the anniversary. If a rule says "the day you turn 18," compute the anniversary, not the year number alone.
- Leaving as-of blank near midnight. If you are close to the change of date, type the as-of date so the result matches the calendar day you mean.
Limitations
Dates only. No hour of birth, no time zone database, and no gestational age. The tool does not store the date you type. It does not apply school-entry cutoffs, insurance rules, or retirement law. Leap-day birthdays are exact on leap years and only approximate on the next-birthday line in other years. For a generic span with business days, use date difference. For a ticking countdown to a party, use the Countdown Calculator.
This is a calendar tool, not medical, legal, or financial advice. A clinician dates a pregnancy with clinical rules. A benefits decision follows the agency's rules. Use the numbers here as the arithmetic input to those rules.
FAQ
Why not just the number of years?
Completed years are the first part of the result, and many forms stop there. Infant records, some court forms, and "how many days until I turn 30" questions need the months, the days, or the next-birthday count as well.
Does a leap day make someone a year older?
No. A leap day inside the span adds one day to the total-day count. The year of age still changes on the birthday. From a first birthday to the next is one year whether or not 29 February occurred in between.
Can I calculate someone else's age?
Yes. The formula does not depend on whose birthday it is. The page does not keep a list of dates after you leave it.
How is this different from the date difference calculator?
Age adds the spoken years-months-days form, the expanded hours and minutes, and the next birthday. Date difference adds a business-day count and is aimed at any two dates, such as a contract. Use age when one of the dates is a birth date and you care about the birthday.
What if I was born on 29 February?
In a leap year the anniversary is 29 February. In other years the next-birthday figure may use 1 March. Say which date your family or your paperwork treats as the anniversary if that choice matters for a deadline.
Practical tips
For a form, copy the years, months, and days line and ignore the hour figure unless the form asks for days or weeks of life. Set the as-of date to the date the form will be read, especially if you are filling it out early. For an infant under a few days old, the day count is meaningful and the hour count is only days × 24, so add the clock time by hand if a hospital form wants hours.
If you are comparing two people's ages, run the calculator twice with the same as-of date. Subtracting birth years is wrong whenever one birthday has passed and the other has not.
Keep legal and benefits questions attached to the official source. An age result tells you that a birthday has or has not arrived. The Social Security estimator and your plan documents tell you what that birthday changes.