Dog Age in Human Years Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
A dog's age in equivalent human years is calculated as 16 × ln(dog's age) + 31, a formula published in 2020 from DNA methylation profiles — far more accurate than the old 'multiply by 7' rule. A 2-year-old dog therefore corresponds to about 42 human years.
Explanation
The popular rule of multiplying a dog's age by 7 is a crude, scientifically outdated approximation: it assumes a constant aging speed throughout life, whereas a dog actually ages very fast in its first year (a one-year-old puppy has already reached a maturity comparable to a young human adult) and much more slowly afterward. In 2020, a team from the University of California, San Diego (Wang, Ideker et al., published in Cell Systems) proposed a formula based on comparing DNA methylation profiles between dogs and humans — a biological measure of aging, closer to real biological age than a simple year count. This formula, 16 × ln(dog's age) + 31, mathematically captures this fast-then-slow progression: a one-year-old dog equals about 31 human years, a 2-year-old dog about 42 years, but each additional year then adds an increasingly smaller gap. **Important limitation**: this study was conducted exclusively on Labrador Retrievers. Aging speed varies considerably by breed and especially by dog size — larger breeds generally age faster and have a shorter life expectancy than smaller breeds. This calculator therefore gives a useful estimate, much better grounded than the '×7' rule, but remains an approximation, not an individual measurement of your dog's actual biological age. For a similarly evidence-based estimate for a different pet, see also our cat age in human years calculator, which relies on a widely cited veterinary rule of thumb rather than an equivalent DNA study.
Example: a 2-year-old dog
Inputs
Dog's age: 2 years.
Calculation
Equivalent human age = 16 × ln(2) + 31 = 16 × 0.6931 + 31 ≈ 11.09 + 31 ≈ 42.09.
Result
A 2-year-old dog corresponds to about 42 human years under this formula.
Frequently asked questions
Why not use the 'dog's age × 7' rule anymore?
Because it assumes linear, constant aging, which doesn't match real biology: a dog reaches most of its physical maturity within its first year, a progression far faster than a simple factor of 7 would suggest. The logarithmic formula better reflects this rapid growth followed by a slowdown.
Does this formula work for all dog breeds?
It was established from Labrador Retrievers only, a medium-to-large breed. Smaller breeds generally age more slowly and live longer than larger breeds, so the actual equivalence may differ noticeably for a chihuahua or a Great Dane, for example, even though the general shape of the curve (fast then slow) is probably similar.
What happens for a puppy under one year old?
The formula becomes less reliable below one year, because the logarithm of a number close to zero tends toward very negative values, which doesn't correspond to actual negative aging. This calculator deliberately limits input to a minimum of one year for this reason.