How the age calculation works
- Years: the number of birthdays that have passed on or before the “age at” date.
- Months: whole months since the most recent birthday.
- Days: the remaining days after those whole months.
Leap years are handled automatically. Totals (days, weeks, hours) count the exact number of calendar days between the two dates.
Example: Someone born on May 15, 1990 is 36 years, 4 months and 13 days old on September 28, 2026 — a total of 13,285 days. Their next birthday, May 15, 2027, is 229 days away.
Age in different cultures
This calculator uses the international (Western) system, in which you are 0 at birth and gain a year on each birthday. Some East Asian traditions count a baby as one year old at birth and add a year at the new year; South Korea officially moved to the international system for legal purposes in 2023.
Need the time between any two dates instead? Use the days between dates calculator.
Frequently asked questions
How is exact age calculated?
Count the full years since birth, then the full months since the last birthday, then the remaining days. Because months have different lengths, “one month” is counted from a date to the same date in the next month (or the last day of that month if it is shorter).
When does someone born on February 29 have a birthday?
In non-leap years this calculator treats February 28 as the birthday, which is the convention used in many places. Legal rules vary by country: some treat March 1 as the birthday for purposes such as age of majority.
How many days old am I?
Enter your birth date — the result shows your age in total days, weeks, months and hours as well as in years, months and days.
Can I calculate age on a past or future date?
Yes. Change the “Age at this date” field to any date to find someone’s age on that day — for example, on a school cut-off date or at retirement.