Age In Years Calculator

How to Calculate Your Age in Years

Whole years tell you how old you are at a birthday; decimal years tell you how much time has actually passed. The Age in Years Calculator reports your age as a precise decimal by using the average length of a calendar year.

How the Calculation Works

The tool takes the total days lived and divides by 365.25, the average number of days in a Gregorian year once leap days are spread evenly:

$$Y = \frac{D}{365.25}$$

The result is shown to four decimal places, so you can see the small fraction between one birthday and the next.

Worked Example

Enter June 15, 1990 as the birth date and June 15, 2021 as the reference date. Exactly 31 calendar years have passed, which is 11,323 days because the span includes eight leap days. Dividing by 365.25 gives:

$$Y = \frac{11{,}323}{365.25} = 31.0007 \text{ years}$$

The value sits just above 31 because 31 calendar years hold slightly more days than 31 times 365.25. For a whole-unit breakdown, use the Age in Years, Months and Days Calculator or the Age in Months Calculator.