What “human years” means here
An age conversion is a rough comparison of development and aging. It does not measure biological age, diagnose a condition, or estimate time left. Dog and cat calculations retain their published reference charts. Rabbit, hamster, guinea pig, ferret, and horse calculations use selected published educational comparison models. None of these numbers is a clinical measurement.
Dogs
Dog age reference by adult weight
The dog calculator uses the American Kennel Club’s published size-group chart. Choose by fully grown weight: small is 20 lb or less, medium is 21–50 lb, large is 51–100 lb, and giant is over 100 lb. Approximate kilogram equivalents are 9, 23, and 45 kg at those cutoffs.
Unlike the smaller groups, giant dogs begin at 12 human years for age one and 22 for age two in this particular chart. We preserve those source values. The calculator supports one to sixteen years and does not extend the table to younger puppies or older dogs.
| Pet years | Small dog | Medium dog | Large dog | Giant dog |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
Cats
Cat age reference chart
The cat calculator follows International Cat Care’s age chart. A cat is about 15 in human years at one year old, 24 at two, then gains about four human years per cat year. The source chart extends to 25 actual years.
| Actual months | Human years |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 6 |
| 5 | 8 |
| 6 | 10 |
| 7 | 12 |
| 12 | 15 |
| 18 | 21 |
| 24 | 24 |
| Pet years | Human years |
|---|---|
| 1 | 15 |
| 2 | 24 |
| 3 | 28 |
| 4 | 32 |
| 5 | 36 |
| 6 | 40 |
| 7 | 44 |
| 8 | 48 |
| 9 | 52 |
| 10 | 56 |
| 11 | 60 |
| 12 | 64 |
| 13 | 68 |
| 14 | 72 |
| 15 | 76 |
| 16 | 80 |
| 17 | 84 |
| 18 | 88 |
| 19 | 92 |
| 20 | 96 |
| 21 | 100 |
| 22 | 104 |
| 23 | 108 |
| 24 | 112 |
| 25 | 116 |
Rabbit
Selected comparison nodes
The Bunny Lady: Rabbit Years to Human Years — published age table.
The published table is used as written, including 62 at eight years and 66 at nine. Its adult entries differ from the article’s general six-year increment. These are educational comparison values, not a validated biological-age measurement.
Supported input: 1 month to 15 years. No values outside this range are extrapolated.
| Actual months | Human years |
|---|---|
| 1 | 3 |
| 2 | 6 |
| 3 | 9 |
| 4 | 12 |
| 5 | 13 |
| 6 | 14 |
| 7 | 15 |
| 8 | 16 |
| 9 | 17 |
| 10 | 18 |
| 11 | 19 |
| 12 | 20 |
| 24 | 26 |
| 36 | 32 |
| 48 | 38 |
| 60 | 44 |
| 72 | 50 |
| 84 | 56 |
| 96 | 62 |
| 108 | 66 |
| 120 | 72 |
| 132 | 78 |
| 144 | 84 |
| 156 | 90 |
| 168 | 96 |
| 180 | 102 |
Hamster
Selected comparison nodes
CalculationDesk: Hamster Age Calculator — Age & Life Stage Conversion Table.
This general hamster comparison table is used without adding species-specific adjustments. Its listed nodes are consistent with its piecewise formula; inconsistent senior-age prose is not used. It is an educational model rather than a veterinary standard.
Supported input: 1 month to 3 years. No values outside this range are extrapolated.
| Actual months | Human years |
|---|---|
| 1 | 14 |
| 3 | 15.6 |
| 6 | 18 |
| 12 | 30 |
| 18 | 43.5 |
| 24 | 57 |
| 36 | 82 |
Guinea Pig
Selected comparison nodes
FreeSmartCalculator: Guinea Pig Years to Human Years Calculator — Guinea Pig Age Chart.
This selected two-phase comparison chart assigns twenty human years at one guinea pig year, followed by ten per year. It is not the conflicting fifty-year first-year example in the shared discussion, and is not a clinically validated equivalence.
Supported input: 3 months to 8 years. No values outside this range are extrapolated.
| Actual months | Human years |
|---|---|
| 3 | 5 |
| 6 | 10 |
| 12 | 20 |
| 24 | 30 |
| 48 | 50 |
| 72 | 70 |
| 96 | 90 |
Ferret
Selected comparison nodes
FurCalc: Ferret Age Calculator — Ferret-to-human age conversion table.
The labeled conversion table is used instead of conflicting calculator helper text on the source page. The open-ended eight-plus-year entry is used only at eight years; older ages are not extrapolated. The comparison is educational, not a veterinary consensus claim.
Supported input: 2 months to 8 years. No values outside this range are extrapolated.
| Actual months | Human years |
|---|---|
| 2 | 5 |
| 6 | 10 |
| 12 | 15 |
| 24 | 28 |
| 36 | 38 |
| 48 | 50 |
| 60 | 60 |
| 72 | 70 |
| 84 | 80 |
| 96 | 90 |
Horse
Selected comparison nodes
University of Georgia Extension: Older Equine Care — Aging Gracefully age comparison table (slide 5).
The comparison starts at two human years for a newborn horse, then eight, thirteen, seventeen and twenty at horse ages one to four. The listed 2.5-year annual increment after age four reaches seventy at age twenty-four. The slide’s rounded five-year range label is not a separate node. This is a life-stage analogy, not measured biological age.
Supported input: 1 month to 24 years. No values outside this range are extrapolated.
| Actual months | Human years |
|---|---|
| 0 | 2 |
| 12 | 8 |
| 24 | 13 |
| 36 | 17 |
| 48 | 20 |
| 288 | 70 |
How we handle extra months
When an age falls between two published points, we use linear interpolation: we take the same fraction of the difference between their human-age values. This is a convenient estimate made by this calculator, not a claim that real biological aging is linear.
For example, the large-dog chart lists 61 at age nine and 66 at age ten. At nine years and six months, we estimate 63.5 human years. For cats, we also use the intermediate kitten and eighteen-month points rather than drawing a single line through the first two years.
Values are shown to at most one decimal place. A decimal describes the calculation, not its biological precision. The tool accepts whole years and 0–11 extra months.
Why we don’t use one formula for every pet
Dogs, cats, and other species develop differently. Even among dogs, size and breed affect aging. The logarithmic dog-age formula discussed in some research was developed from Labrador Retriever data; we do not present it as a universal model for every dog.
Seven species are supported. The selected exotic-pet models are published comparisons, not a unified veterinary standard. Where a source page contains conflicting prose, calculator helper text, or range examples, the selected table and the resolution are explicitly documented above. No midpoints are chosen from conflicting coefficient ranges, and lifespan ratios are not invented by this site.
Sources and selected nodes reviewed on October 27, 2026. Pet Age Convertor is an independent tool and is not affiliated with or endorsed by these organizations.