Age Calculator
Calculate exact age in years and total days lived from any birth date, as of today or any date you choose.
Fill in the required fields to see your result.
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Age in years is rounded down (you're not a year older until the full year has passed) — total days is the exact count.
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How Exact Age Is Calculated
Your exact age combines two numbers: total days lived, and age in completed years. Total days is a straight count between your birth date and today (or any date you choose). Years uses 365.25 days per year to account for leap years.
How to Calculate Exact Age
Total Days = As-Of Date − Birth Date. Age in Years = FLOOR(Total Days ÷ 365.25).
Age Calculator Formula
- Total Days = As-Of Date − Birth Date
- Age (Years) = FLOOR(Total Days ÷ 365.25)
Why Is Age Rounded Down?
Because you're not considered a year older until your full birthday has actually passed — age in years always rounds down to the last completed year, never up.
Age Calculation Examples
Born January 1, 2000, as of July 12, 2026: Total days = 9,689. Age = FLOOR(9,689 ÷ 365.25) = 26 years.
Common Age Calculation Mistakes
Using 365 instead of 365.25 days per year, which drifts noticeably wrong over a long lifespan due to leap years. Forgetting time zones can shift a "today" calculation by a day near midnight, though this calculator treats both dates as calendar dates without time-zone adjustment. Assuming age changes immediately at a birthday in a different time zone than where you're calculating from.
How to Use This Calculator
Enter the birth date and the date to calculate age as of (defaults to today).
Formula & Methodology
Total days between the two dates is calculated directly, then converted to years using 365.25 days per year to account for leap years.
Example: born January 1, 2000, as of January 1, 2026
9,497 days have passed (accounting for leap days) ≈ 26.0 years old.
Counts whole calendar days between the two dates. Time zone is not factored in — both dates are treated as calendar dates.
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Frequently Asked Questions
- How is exact age calculated?
- The total number of days between your birth date and today (or any date you choose) is calculated, then converted to years using 365.25 days per year to account for leap years.
- Why is age rounded down?
- You're not considered a year older until your full birthday has passed — so age in years always rounds down to the last completed year.
- Can I calculate my age as of a future or past date?
- Yes — change the 'as of' date to any date you want to check your age against.
Last updated 7/15/2026