Convert your pet's age to human years using the latest veterinary aging charts.
Dog
Cat
Small (20 lbs or less)
Medium (21-50 lbs)
Large (51-90 lbs)
Giant (Over 90 lbs)
Your pet's age in human years is approximately:
How Pet Age is Really Calculated
For decades, the common rule of thumb was that one "dog year" equaled seven human years. However, modern veterinary science tells a different story. Pets age much faster in their first two years of life and then the aging process stabilizes based on their species and size.
Our calculator uses the American Veterinary Medical Association (AVMA) guidelines which suggest that the first year of a medium-sized dog's life is roughly equal to 15 human years. The second year adds about nine more human years, making a 2-year-old pet roughly 24 in human terms. After that, each year for a dog is approximately 4 to 7 years depending on their weight.
Dog Age Calculation by Size
Pet Age
Small Dog
Medium Dog
Large Dog
Cat
1 Year
15
15
15
15
2 Years
24
24
24
24
5 Years
36
37
40
36
10 Years
56
60
66
56
Examples of Aging Calculations
Example 1: A 5-year-old cat is roughly 36 human years old. (15 + 9 + 4 + 4 + 4).
Example 2: A 10-year-old Great Dane (Giant) is roughly 78 human years old due to the faster metabolic aging of large breeds.
Example 3: A 3-year-old Chihuahua (Small) is roughly 28 human years old.
Why Do Larger Dogs Age Faster?
It is a biological anomaly that larger mammals usually live longer (like elephants vs. mice), yet in the canine world, larger breeds age faster. Researchers believe this is because larger dogs grow from puppies to adults at an accelerated rate, which may lead to a higher likelihood of abnormal cell growth and age-related diseases earlier in life.
function calculatePetAge() {
var petType = document.getElementById('petType').value;
var dogSize = document.getElementById('dogSize').value;
var petAge = parseFloat(document.getElementById('petAge').value);
var humanAge = 0;
var resultBox = document.getElementById('result-box');
var resultDisplay = document.getElementById('humanAgeResult');
var lifeStage = document.getElementById('lifeStage');
if (isNaN(petAge) || petAge < 0) {
alert("Please enter a valid age.");
return;
}
if (petType === 'cat') {
if (petAge === 0) {
humanAge = 0;
} else if (petAge <= 1) {
humanAge = petAge * 15;
} else if (petAge <= 2) {
humanAge = 15 + ((petAge – 1) * 9);
} else {
humanAge = 24 + ((petAge – 2) * 4);
}
} else {
// Dog Calculation
if (petAge === 0) {
humanAge = 0;
} else if (petAge <= 1) {
humanAge = petAge * 15;
} else if (petAge <= 2) {
humanAge = 15 + ((petAge – 1) * 9);
} else {
var factor = 4;
if (dogSize === 'small') factor = 4;
else if (dogSize === 'medium') factor = 5;
else if (dogSize === 'large') factor = 6;
else if (dogSize === 'giant') factor = 7;
humanAge = 24 + ((petAge – 2) * factor);
}
}
var roundedAge = Math.round(humanAge * 10) / 10;
resultDisplay.innerHTML = roundedAge + " Human Years";
// Determine life stage
var stage = "";
if (roundedAge < 12) stage = "Life Stage: Puppy/Kittenhood";
else if (roundedAge < 25) stage = "Life Stage: Adolescent";
else if (roundedAge < 50) stage = "Life Stage: Adult";
else if (roundedAge < 70) stage = "Life Stage: Mature/Senior";
else stage = "Life Stage: Geriatric";
lifeStage.innerHTML = stage;
resultBox.style.display = 'block';
}