Age & Time

Dog Age Calculator

Find your dog's age in human years using the modern veterinary age-conversion method.

2 min 100% free No sign-up

Your dog's birthdate

Don't know the exact day? Your best guess works fine — this is an estimate, not a vet visit.

Breed size

Size changes the math: bigger dogs age faster in the conversion models.

Conversion model

Estimated age in human years

– human years

Exact age–

Life stage–

Next birthday–

How it works

Why "multiply by 7" doesn't work

The old rule — one dog year equals seven human years — is easy to remember and mostly wrong. A one-year-old dog is already a young adult, not a seven-year-old child, and a fifteen-year-old dog is far older than a 105-year-old person would be. Dogs mature explosively in their first two years and then settle into a steadier pace, so any honest conversion has to treat those early years differently. That is exactly what both models on this page do.

The simple size-based model

The simple model counts 15 human years for the first year of a dog's life and 9 for the second — that covers the fast-maturing puppy and adolescent phase. After that, it adds a fixed number of human years per dog year depending on size: 4 for small breeds, 5 for medium, 6 for large, and 7 for giant breeds. So a four-year-old medium dog lands at 15 + 9 + 5 + 5 = 34 human years, while a four-year-old giant breed lands at 15 + 9 + 7 + 7 = 38. The size adjustment exists because breeds of different sizes are observed to move through life stages at different speeds.

The modern logarithmic model

The modern formula — human age = 16 × ln(dog years) + 31 — comes from canine aging research published by scientists at UC San Diego, who compared age-related changes in dog and human DNA. Because it is logarithmic, it captures the real shape of a dog's life: huge leaps in the early years, then a long, gentle slope. A one-year-old dog converts to about 31 human years under this model, a four-year-old to about 53, and a ten-year-old to about 68. Note that this formula does not adjust for breed size, which is why very small and very large dogs can look "older" or "younger" here than the simple model suggests.

Which number should you trust?

Neither is a medical measurement — both are estimates built for fun and planning. Use the simple model when you want a number that respects breed size, and the modern model when you want the figure backed by published aging research. If the two disagree by a lot, that disagreement is itself informative: it usually means size is doing heavy lifting in the simple model, as with giant breeds.

What the result actually means

Treat the human-year number as a conversation starter, not a diagnosis. A "senior" label doesn't mean your dog is unwell — many dogs are at their sweetest, calmest, and most devoted in those years. What the label is good for is practical planning: adjusting play intensity, thinking ahead about comfort, and appreciating which chapter of the story you're in. For anything about your individual dog's health, your vet — who knows your dog — beats any formula on the internet.

Worked example

Example: Bella is a Labrador (large breed) who just turned 4. Under the simple model: 15 (year one) + 9 (year two) + 6 + 6 (two large-breed years) = 36 human years. Under the modern model: 16 × ln(4) + 31 ≈ 16 × 1.386 + 31 ≈ 53 human years. Her life stage is Adult (large breeds shift to Senior at 6), and if her birthday is March 10, the countdown tells you exactly how many days until the next one.