Small (20 lbs or less)
Medium (21-50 lbs)
Large (51-90 lbs)
Giant (Over 90 lbs)
Your dog's age in human years is:
0
function calculateDogAge() {
var actualAge = parseFloat(document.getElementById('dogActualAge').value);
var weightClass = document.getElementById('dogWeightClass').value;
var resultDiv = document.getElementById('dogAgeResult');
var resultVal = document.getElementById('humanYearsValue');
var stageText = document.getElementById('lifeStageText');
if (isNaN(actualAge) || actualAge 0 && actualAge 1 && actualAge 2) {
// Base calculation for first 2 years = 24 years
humanYears = 24;
var remainingYears = actualAge – 2;
// Rates differ by size after year 2
if (weightClass === 'small') {
humanYears += remainingYears * 4;
} else if (weightClass === 'medium') {
humanYears += remainingYears * 5;
} else if (weightClass === 'large') {
humanYears += remainingYears * 6;
} else if (weightClass === 'giant') {
humanYears += remainingYears * 7;
}
}
resultVal.innerHTML = Math.round(humanYears * 10) / 10 + " years";
// Life Stage Logic
var stage = "";
if (humanYears < 12) stage = "Puppyhood";
else if (humanYears < 25) stage = "Junior / Adolescent";
else if (humanYears < 50) stage = "Adult";
else if (humanYears < 70) stage = "Mature Adult";
else stage = "Senior / Geriatric";
stageText.innerHTML = "Life Stage: " + stage;
resultDiv.style.display = "block";
}
How to Calculate Your Dog's Age in Human Years
The old "multiply by seven" rule for dog years is actually a myth. Scientific research into canine aging has shown that dogs age much faster in their first two years of life than humans do, and their aging process slows down or accelerates later based on their breed size.
The Modern Aging Formula
Veterinarians generally agree on a more nuanced approach to calculating canine age. For most breeds, the first year of a dog's life is equivalent to roughly 15 human years. The second year adds about 9 human years. From that point forward, the rate of aging depends heavily on the dog's weight and size.
Small Breeds: Generally live longer and age about 4 human years for every calendar year after age 2.
Medium Breeds: Age approximately 5 human years for every calendar year after age 2.
Large Breeds: Age roughly 6 human years for every calendar year after age 2.
Giant Breeds: Age the fastest, roughly 7 human years for every calendar year after age 2.
Dog Age Chart by Size
Dog's Actual Age
Small (Human Years)
Medium (Human Years)
Large (Human Years)
1 Year
15
15
15
2 Years
24
24
24
5 Years
36
39
42
10 Years
56
64
72
15 Years
76
89
102
Factors Affecting Canine Longevity
While the calculator provides a statistical estimate, several factors influence how your individual dog ages:
Genetics: Specific breeds are prone to different health conditions that can impact biological aging.
Nutrition: High-quality, balanced diets prevent obesity, which is one of the leading causes of premature aging in dogs.
Dental Health: Periodontal disease can lead to heart and kidney issues, effectively "aging" the dog's organs faster.
Exercise: Regular physical activity maintains muscle mass and cognitive function well into the senior years.
Example Calculations
Example 1: A 4-year-old French Bulldog (Small Class). The first two years equal 24 human years. The next two years add 4 years each. 24 + 4 + 4 = 32 human years.
Example 2: An 8-year-old Great Dane (Giant Class). The first two years equal 24 human years. The next six years add 7 years each. 24 + (6 x 7) = 66 human years.