“How old are you?” usually gets an answer in whole years, but forms, school enrollment, medical charts and plain curiosity often need more precision. This age calculator gives an exact age in years, months and days, totals in months, weeks, days and hours, the weekday you were born, and a countdown to your next birthday.
How to use the age calculator
- Enter the date of birth.
- Leave Age on this date set to today, or pick any other date to find an age in the past or future.
- If the birth date is February 29, choose whether the birthday counts on February 28 or March 1 in common years.
The tape shows the exact age first, followed by running totals and your next birthday. The milestones table lists dates such as your 10,000th day and your billionth second.
How age is calculated
Ages are counted by anniversaries, the same way people count them in everyday life:
- Years: the number of birthdays that have passed.
- Months: whole monthly anniversaries since the last birthday.
- Days: the calendar days left over until the “age on” date.
When a monthly anniversary falls on a day the month does not have, such as the 31st of a 30-day month, it is moved to the month’s last day. That keeps every part of the answer positive and consistent with how the date calculator adds months.
Totals in other units
Total days are a simple subtraction of the two dates. Weeks are total days ÷ 7, and total months are the years × 12 plus months from the exact age. Hours and minutes multiply the days by 24 and 1,440, treating both dates as midnight.
Worked example
Born June 15, 1990, age on October 11, 2026:
- The 36th birthday was June 15, 2026, so the age is 36 years.
- Three monthly anniversaries have passed since then (July 15, August 15, September 15): 3 months.
- From September 15 to October 11 is 26 days.
- Total days: 13,267, which is 1,895 weeks and 2 days, 435 months and 26 days, or 318,408 hours.
- June 15, 1990 was a Friday, and the next birthday, the 37th, is Tuesday, June 15, 2027, 247 days away.
Edge cases worth knowing
| Situation | How it is handled |
|---|---|
| Born on the 31st | Monthly anniversaries in shorter months fall on the last day of that month |
| Born February 29 | Birthday counted on February 28 or March 1 in common years (your choice) |
| Age on the birthday itself | Counts as the new age; the next birthday is a year away |
| “Age on” date before birth | Not allowed; pick a later date |
Age in different traditions
The calculator uses the international convention, where you are 0 at birth and gain a year on each birthday. Under traditional East Asian age reckoning a baby is 1 at birth and gains a year at the new year, so a person’s traditional age can be one or two years higher. South Korea adopted the international method for legal and official purposes in 2023.
To check whether someone meets a minimum age on a particular date, such as 21 for alcohol purchases, use the age checker. For birthday weekdays and half-birthdays, try the birthday calculator.
Frequently asked questions
How is exact age calculated?
Count the whole years since the last birthday, then the whole months since the last monthly anniversary, then the remaining days. Someone born June 15, 1990 is 36 years, 3 months and 26 days old on October 11, 2026.
How do you count age for someone born on February 29?
In leap years the birthday is February 29. In common years you can choose February 28, which keeps the birthday in February, or March 1, the day after February 28. Legal conventions differ by place and purpose, so the calculator lets you pick.
Why are hours and minutes only approximate?
The calculator works in whole calendar days and assumes a birth at midnight. If you were born in the afternoon, you reach each hour total later by that many hours.
Can I calculate an age on a past or future date?
Yes. Change the Age on this date field to any date after the birth date, for example to find how old someone was on their wedding day or will be at retirement.
What does the 1 billion seconds milestone mean?
One billion seconds is 11,574 days, 1 hour, 46 minutes and 40 seconds, or about 31.7 years. The milestones table shows the date you pass it, assuming a midnight birth.