SumAge Calculator
Find your exact age in years, months and days — plus how many days you have lived, the day of the week you were born, and how long until your next birthday.
Your exact age
How It Works
Your age is not just the current year minus your birth year — the months and days matter too. This calculator compares your date of birth with the "as of" date and works out the difference in whole years first, then the remaining whole months, then the remaining days. If your birthday has not happened yet in the current year, one year is subtracted; if the day of the month has not been reached yet, a month is borrowed and the days are counted from the previous month. That is why the result is exact rather than an estimate.
Leap years are handled automatically because the calculation uses real calendar dates, not an average year length. A person born on February 29, for example, still ages one year every year — in non-leap years their birthday is treated as March 1 for the "days until next birthday" count. The total days lived is a straight count of calendar days between the two dates, which is also how the total weeks and total months figures are derived (weeks = days ÷ 7, months ≈ days ÷ 30.44, the average length of a month).
Worked example: someone born on June 15, 1990, checking their age on November 12, 2026, is 36 years, 4 months and 28 days old. They were born on a Friday, have lived 13,299 days, and their next birthday (June 15, 2027) is 215 days away. You can verify the years yourself: 2026 − 1990 = 36, and since June 15 has already passed in 2026, no year is subtracted. From June 15 to November 12 is 4 months (June 15 → October 15) plus 28 days (October 15 → November 12).
Frequently Asked Questions
How is my exact age calculated?
We subtract your birth date from the "as of" date using real calendar rules: whole years first, then whole months, then remaining days, borrowing from the previous month when the day of the month has not been reached yet. Leap years are included automatically.
What happens if I was born on February 29?
You still turn one year older every year. For the "days until next birthday" count, in non-leap years the birthday is treated as March 1, which is the convention most age calculators use.
Can I calculate my age on a different date?
Yes. Change the "Calculate age as of" field to any past or future date — for example, to find out how old you will be on a wedding date, a retirement date, or a child's first day of school.
Why does the total months figure differ from years × 12 + months?
It should not differ by much. The exact age (years, months, days) uses calendar months, while "total months" is an approximation: total days ÷ 30.44, the average month length. Small differences of a day or two are normal because months are 28–31 days long.
Is my date of birth stored anywhere?
No. The calculation runs entirely in your browser and your date of birth is never sent to a server or saved.
Last updated: November 2026