How to use the age calculator
- Enter the date of birth.
- Leave Age on this date set to today, or change it to find how old someone was, or will be, on another day.
- Read the age in years, months and days. Below it are the same age as a total number of months, weeks, days and hours, the weekday of birth, and the next five birthdays.
How age is calculated
The calculator counts forward from the date of birth in whole calendar months, then counts the days that are left over:
"Birth date + k months" means the same day of the month, k months later. When that day doesn't exist, the last day of the month is used instead: one month after January 31 is February 28, or February 29 in a leap year. The total in days is an exact count of calendar days, so leap years are included automatically. Hours are the total days times 24; the calculator works with calendar dates, so the hour of birth and daylight saving changes are not part of it.
Worked example
The calculator opens with a date of birth of May 15, 1990 and today's date. Taking October 29, 2026 as the age-on date:
- Whole years: May 15, 1990 to May 15, 2026 is 36 years.
- Whole months: May 15, 2026 to October 15, 2026 is 5 months.
- Days left: October 15 to October 29 is 14 days.
- The age is 36 years, 5 months, 14 days, or 437 months and 14 days.
- Total days: 36 × 365 + 9 leap days = 13,149 days to the 36th birthday, plus 167 days since then, for 13,316 days. That is 1,902 weeks and 2 days, or 319,584 hours.
- May 15, 1990 was a Tuesday. The next birthday is Saturday, May 15, 2027, the 37th, which is 198 days away.
Birthdays on February 29
Someone born on a leap day has a real birthday only once every four years. This calculator counts February 28 as the birthday in other years, so the age goes up on February 28. For example, a person born on February 29, 2000 is 26 years old on February 28, 2026. Some laws count March 1 instead, which can matter for things like a driving license or a pension start date. If you need the legal date, check the rule where you live.
Ages in different systems
| System | How the age is counted | Example: born May 15, 1990, on Oct 29, 2026 |
|---|---|---|
| Western (this calculator) | Starts at 0 and goes up on each birthday | 36 |
| Months and days | Whole months, then remaining days | 437 months, 14 days |
| Traditional East Asian | Starts at 1 and goes up every new year | 37 |
Most official uses, including school entry, voting and retirement, follow the Western count.
Frequently asked questions
How do I calculate my age in days?
Count the days from your date of birth to today, including every February 29 in between. Someone born May 15, 1990 is 13,316 days old on October 29, 2026. The calculator shows this total under the main answer.
Why does a one-month age sometimes cover only 28 days?
Months have different lengths, so "one month" means the same date in the next month, not a fixed number of days. From January 31 the next monthly mark is February 28, because February has no 31st. That is the same rule used for adding months in the date calculator.
Can I find the age at a past or future date?
Yes. Change the Age on this date field to any date after the birth date. This is useful for questions like "How old was my grandmother in 1975?" or "How old will I be when I retire on a set date?"
Does the time of birth matter?
Only on the birthday itself. The calculator works in whole days, so on the morning of your birthday it already counts the new year of age, even if you were born late at night. For a precise count of hours and minutes, use the time duration calculator with the birth time.
Related calculators
- Date Calculator — Add or subtract years, months, weeks and days from a date, or count the days and weekdays between two dates.
- Day Counter — Count the days or weekdays between two dates, with or without the end date, or count down the days to an event.
- Day of the Week Calculator — The weekday for any date from the year 1 to 9999, worked out step by step with Zeller's congruence and the Doomsday rule.
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