Age Calculator
Your age is more than a single number. This calculator counts the exact years, months and days between two dates, converts the span into total months, weeks, days and hours, tells you the weekday you were born and counts down to your next birthday. Leave the second date blank to use today.
How to use the age calculator
- Pick your date of birth.
- Leave the second date blank to calculate your age today, or choose another date to see your age then.
- Read your age and the extra facts below it.
Formula
The calculator subtracts year, month and day in turn, borrowing the length of the previous month when the day difference is negative. Total days is the difference between the two dates divided by 86,400,000 milliseconds. Leap days are counted automatically.
Worked examples
A leap-day birthday
Born 29 February 2000, on 1 March 2024 the age is 24 years, 0 months and 1 day.
A regular date
Born 15 May 1990, on 26 September 2026 the age is 36 years, 4 months and 11 days, and the next birthday is 231 days away.
Counting age accurately
Why it is harder than subtracting years
Someone born in May 1990 is 36 in September 2026, but in March 2026 they would still be 35. Exact age depends on whether the birthday has occurred yet this year, and the number of days in each month varies.
Leap years
A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year but 1900 was not. A person born on 29 February has a birthday on that date only every four years, and many legal systems treat 28 February or 1 March as the birthday in other years.
Fun ways to see your age
| Milestone | Days |
|---|---|
| 1 billion seconds | about 11,574 days (31.7 years) |
| 10,000 days | about 27.4 years |
| 20,000 days | about 54.8 years |
Everyday uses
Checking eligibility for a school or a benefit, planning a milestone birthday, or working out the age gap between two people. For date arithmetic beyond this, remember that an “as of” date lets you see anyone’s age on any day, in the past or future.
Practice problems
Try these yourself first, then check your answer. The answers come from the calculator above.
- Born 12 March 2005. What is the age on 1 January 2026?
Show answer
Age: 20 years, 9 months, 20 days
- Born 29 February 2004. What is the age on 28 February 2026?
Show answer
Age: 21 years, 11 months, 30 days
Common mistakes to avoid
- Counting only the difference in years, which ignores whether the birthday has passed this year.
- Forgetting leap years when counting days by hand.
- Entering the day and month in the wrong order. Use the date picker to avoid this.
Frequently asked questions
How do I calculate my exact age?
Subtract the birth date from the target date, borrowing months and days as needed. This calculator does it for you.
How many days old am I?
The “Total days” row shows the exact figure between the two dates.
Does it handle leap years?
Yes. All dates are counted on the real calendar.
Is my date stored anywhere?
No. The calculation runs in your browser and nothing is sent to a server.
Reviewed September 26, 2026 by the SolveCalcPro editorial team. Found a mistake? Tell us; see our editorial policy.