How to use the dog age calculator
- Dog's age — whole years plus months. If you know the birth date, the age calculator gives the exact years and months.
- Adult size — pick the weight class your dog is, or will be, when fully grown.
You get three numbers side by side: the AKC size chart, the UC San Diego formula and, for comparison, the old "multiply by 7" rule.
Method 1: the AKC size chart
The American Veterinary Medical Association's general guideline, as the AKC reports it, is that the first year of a medium-sized dog's life equals about 15 human years, the second year about 9 more, and each year after that roughly 5. The AKC turns this into a chart by weight, because large and giant breeds generally have shorter lifespans than small ones and are treated as aging faster after their early years. Small, medium and large dogs share the same values up to age 5; giant dogs start lower (12 at age 1) and then climb fastest.
The chart only covers whole years from 1 to 16. Between rows the calculator interpolates in a straight line (2½ years for a large dog is halfway between 24 and 28, so 26), beyond 16 it extends the last yearly step, and for puppies under 1 it scales the first-year value in proportion.
Method 2: the UC San Diego epigenetic formula
A team led by Tina Wang and Trey Ideker at UC San Diego compared how DNA methylation — chemical tags on DNA that change with age — shifts over time in dogs and in people. They profiled 104 dogs, mostly Labrador retrievers, aged from about 0.1 to 16 years. The study was first posted in 2019 and published in Cell Systems in July 2020 (Wang et al., "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome"). Its age-matching function is:
human age = 16 × ln(dog age) + 31
where ln is the natural logarithm. A logarithm rises steeply at first and then flattens, which captures the idea that dogs race through puppyhood and adolescence and then age more slowly relative to us.
Worked example
A 4-year-old dog: ln(4) ≈ 1.386; 16 × 1.386 ≈ 22.18; 22.18 + 31 = 53.2 human years by the formula. The AKC chart says 32 for a small, medium or large dog and 38 for a giant one. The "× 7" rule says 28.
The methods disagree most for young dogs: at 1 year the formula says 31 and the chart 15. At 10 years they are closer — 67.8 by the formula, 60 to 79 on the chart depending on size.
Dog years to human years chart
| Dog age | Small | Medium | Large | Giant | Formula (Labrador) |
|---|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 | 31 |
| 2 | 24 | 24 | 24 | 22 | 42.1 |
| 3 | 28 | 28 | 28 | 31 | 48.6 |
| 4 | 32 | 32 | 32 | 38 | 53.2 |
| 5 | 36 | 36 | 36 | 45 | 56.8 |
| 6 | 40 | 42 | 45 | 49 | 59.7 |
| 7 | 44 | 47 | 50 | 56 | 62.1 |
| 8 | 48 | 51 | 55 | 64 | 64.3 |
| 9 | 52 | 56 | 61 | 71 | 66.2 |
| 10 | 56 | 60 | 66 | 79 | 67.8 |
| 11 | 60 | 65 | 72 | 86 | 69.4 |
| 12 | 64 | 69 | 77 | 93 | 70.8 |
| 13 | 68 | 74 | 82 | 100 | 72 |
| 14 | 72 | 78 | 88 | 107 | 73.2 |
| 15 | 76 | 83 | 93 | 114 | 74.3 |
| 16 | 80 | 87 | 99 | 121 | 75.4 |
Size columns: AKC chart (small 20 lb or less, medium 21–50 lb, large 51–100 lb, giant over 100 lb). Last column: 16 × ln(age) + 31, rounded.
Limits of both methods
- The formula comes from one breed. The authors note their study focused on Labrador retrievers and that breeds with different lifespans could need different age-translation functions. It has no size adjustment.
- The chart is a rule of thumb. The AVMA presents its figures as a general guideline, not a measurement of any individual dog.
- Neither describes your dog's health. Your veterinarian can tell you when your dog should move to senior checkups.
Frequently asked questions
Is one dog year really seven human years?
No. Both the AKC chart and the UC San Diego formula say dogs age much faster than that in their first two years and more slowly later. A 1-year-old dog is closer to a 15-year-old (chart) or a 31-year-old (formula) human than a 7-year-old.
Which method is more accurate?
Neither is precise for an individual dog. The formula rests on measured DNA changes but only in Labradors; the chart covers sizes but is a general guideline. Looking at both gives a sensible range.
Why does the formula make young dogs so "old"?
The logarithm rises very steeply near the start, matching the study’s finding that dogs change much faster than people early in life.
How old is my puppy in human years?
The AKC chart starts at 1 year, so for puppies this calculator scales the first-year value in proportion. The formula gives a number from about 2 months on. Treat both as rough for puppies.
What size is my mixed-breed dog?
Use the adult weight: small up to 20 lb, medium 21–50 lb, large 51–100 lb and giant over 100 lb. For a puppy, use the expected adult weight — your vet can estimate it.
Last updated: October 8, 2026