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This calculator's estimates your cat's approximate age in human years using a formula based on Purina Pet Expert Team's article. Enter your cat’s current age (in years) or their date of birth, and the calculator will instantly return an approximate human age estimate.


How the formula was made

According to Purina's Pet Expert Team, "...first year of your cat's life is considered the equivalent of 15 human years. The second year adds nine more human years, so 2 cat years are approximately 24 human years. After this, each additional human year is four “cat years” i.e., age 3 will be 28 human years."

So we can deduce that:

To simplify the addition of 4 in years subsequent 2 years, we can make the following function. Let's say x is the cat's age: f(x) = 24 + 4 * (x - 2) We subtract x (the cat's age) by 2 because 24 already accounts for the first two years of the cat's age.

We can simplify further to:

f(x) = 24 + 4 * (x - 2)
f(x) = 24 + 4x - 8
f(x) = 16 + 4x

f(x) = 16 + 4x is the formula I implemented in the JavaScript function calcCatToHumanAge(catAge):

/**
 * converts cat years to human years, using purina's cat-to-human years formula
 * @param {number} catAge - cat age in years.
 * @returns {number} human age in years.
 */
function calcCatToHumanAge(catAge) {
    // from 0 = 0 ... 1 = 15
    // -> 0 <= x <= 1: f(x) = 15x
    if (catAge >= 0 && catAge <= 1) {
        return Math.round(15 * catAge);
    }
    // from 1 = 15 ... 2 = 24
    // -> 1 < x < 2: f(x) = 6 + 9x
    else if (catAge > 1 && catAge <= 2) {
        return Math.round(6 + 9 * catAge);
    }
    // from 2 = 24 ... x = 24 + 4(x - 2)
    // -> x >= 2: f(x) = 16 + 4x
    else if (catAge > 2) {
        return Math.round(16 + 4 * catAge);
    }
}

You can view the full and updated script I wrote here.


Privacy Policy

This website is a fully static site hosted on GitHub Pages. It does not collect, store, or transmit any personal data. All age and date-of-birth input, along with age calculations, are performed entirely on your device using client-side JavaScript. That information never leaves your device and is not sent to any server. The site does not use cookies, analytics, tracking tools, third-party APIs, or CDNs.