What this calculator does
This dog age calculator converts a dog's age in years to a human-equivalent age using the epigenetic-clock formula published by Wang and colleagues in 2020: human age = 16 × ln(dog age) + 31. It is based on measuring chemical changes to DNA over time in both species and lining up the two ageing curves, rather than a fixed multiplier applied to every dog at every age.
The old rule of thumb, multiply a dog's age by seven, is easy to remember but wrong in a way that matters: dogs mature much faster than humans in their first couple of years and then age more slowly per year later on, a curve a flat multiplier cannot capture. The formula used here is logarithmic for that reason, growing quickly at first and levelling out as the dog gets older, which matches how dogs actually age far more closely.
The formula
The formula is human age = 16 × ln(dog age in years) + 31, where ln is the natural logarithm. This produces a curve that rises steeply for a young dog, since a lot of biological ageing happens in the first year or two, and then rises more gradually per additional dog-year as the dog gets older, matching the DNA-methylation ageing pattern the formula was derived from.
| Term | Meaning |
|---|---|
| Epigenetic clock | A method of estimating biological age from chemical changes (DNA methylation) that accumulate on DNA over time. |
| ln | The natural logarithm, the mathematical function behind the fast-then-slowing curve of the epigenetic-clock formula. |
| The old ×7 rule | A once-common approximation (dog age × 7 = human age) that is now considered an oversimplified myth, since it assumes ageing is linear across a dog's whole life. |
The inputs explained
| Field | What to enter |
|---|---|
| Dog's age (years) | The dog's current age in years. Fractional values, such as 0.5 for a six-month-old puppy, are accepted. |
When to use it
Checking a puppy or young dog's development stage
Because the formula rises steeply early on, a one or two-year-old dog already shows a human-equivalent age in the twenties, reflecting how quickly puppies reach physical maturity.
Comparing an older dog's age to a human age bracket
For senior dogs, the curve flattens, so each additional dog-year adds a smaller jump in human-equivalent age than the ×7 rule would suggest.
Explaining why the old ×7 rule gives a different answer
Running the same age through both methods side by side shows how far the flat ×7 multiplier drifts from the epigenetic-clock estimate, especially at the very young and very old ends.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Dog age converted to human-equivalent age
A range of dog ages, each converted using the epigenetic-clock formula.
| Dog age (years) | Human-equivalent age | Dog age in months |
|---|---|---|
| 0.5 | 19.9 years | 6.0 months |
| 1 | 31.0 years | 12.0 months |
| 2 | 42.1 years | 24.0 months |
| 5 | 56.8 years | 60.0 months |
| 10 | 67.8 years | 120.0 months |
| 15 | 74.3 years | 180.0 months |
Questions
How does this dog age calculator work?
It applies the epigenetic-clock formula, human age = 16 × ln(dog age) + 31, based on comparing DNA methylation patterns between dogs and humans as both species age, published by Wang et al. in 2020.
Why not just multiply the dog's age by 7?
The ×7 rule assumes dogs age at a constant rate throughout life, which is not accurate. Dogs mature very quickly in their first couple of years and then age more slowly per year afterwards, a pattern the ×7 rule does not capture.
Is the formula accurate for puppies under a year old?
It is treated loosely below one year, since the epigenetic-clock research it is based on is most reliable from around age one onward; a puppy's development in its first months is faster still than the curve suggests.
Does the formula vary by breed or size?
No, this calculator uses the general formula, which does not adjust for breed or size. Larger breeds are generally understood to age faster in real terms than small breeds, something a single formula cannot capture.
For a cat's age converted the same way, see the cat age calculator. For an expected birth date range instead, see the pet gestation and due date calculator.