How to use the age calculator
Enter your date of birth and, optionally, the date you want to know your age on (it defaults to today). You’ll see your age in years, months and days, plus your total age in months, weeks, days and hours, the day of the week you were born, and a countdown to your next birthday.
How the calculation works
Age in years is the number of complete birthdays that have passed. Months are the complete months since the last birthday, and days are what’s left over. When the day of the month in the target date is smaller than your birth day, the calculator borrows the actual length of the previous month rather than assuming 30 days, so the result is exact.
For example, someone born on January 31 is exactly one month old on February 28 (or 29), and one month and one day old on March 1.
Worked example
Birth date June 15, 1990, checked on August 26, 2026:
| Measure | Value |
|---|---|
| Age | 36 years, 2 months, 11 days |
| Total months | 434 |
| Total weeks | 1,888 |
| Total days | 13,221 |
| Born on a | Friday |
| Next birthday | in 293 days |
Where exact age matters
- Legal thresholds — drinking, voting, driving and retirement ages are all defined in completed years, and the day matters.
- School entry — many districts require a child to be five by a cutoff date such as September 1.
- Insurance and pensions — premiums and benefits are often set by age on a specific date.
- Medical dosing — paediatric doses are frequently given by age in months for children under two.
- Milestones — knowing your 10,000th or 20,000th day makes for an unusual celebration.
Leap years and leap days
A year has 365 days, except leap years with 366 (every year divisible by 4, except century years not divisible by 400 — so 2000 was a leap year, 2100 won’t be). The calculator uses the real calendar, so total-day counts correctly include every leap day you’ve lived through.
Frequently asked questions
How is age calculated?
The calculator counts whole years first, then whole months, then the remaining days, the same way people state their age. Someone born June 15, 1990 is 36 years, 2 months and 11 days old on August 26, 2026.
What if I was born on February 29?
In non-leap years the calculator treats your birthday as February 28 for counting months, and your next birthday as March 1 by convention in most countries. Your total days lived are exact regardless.
Can I calculate age on a past or future date?
Yes. Change the "Age on date" field to any date. It's handy for forms that ask for age on a specific date, such as school enrolment or insurance applications.
Why do different countries count age differently?
Most of the world counts completed years from birth. The traditional East Asian system starts at one at birth and adds a year every New Year. South Korea officially switched to the international system in 2023. This calculator uses the international method.
Last updated August 26, 2026.