Turn your dog's age into human years three ways: the DNA methylation formula from 2020 research, a size-based chart, and the old multiply-by-7 rule. All three sit side by side, with an approximate life stage for your dog's size.
A medium dog aged 5 years is about 39 human years by the size chart, 57 by the DNA methylation formula, and 35 by the multiply-by-seven rule. Approximate life stage: mature adult.
Medium dog, 9 to 23 kg as an adult. Approximate life stage: mature adult
16 × ln(5) + 31 = 56.75
Fitted on Labrador retrievers. It packs a lot of ageing into the first years, then flattens out.
15 + 9 + 5 × 3 = 39
A common rule of thumb: 15 for year one, 9 for year two, then 5 a year for a medium dog.
5 × 7 = 35
Ignores size and treats every year alike. 4 years under the size chart here.
Three estimates, not one answer. Breed, size, and health matter more than any formula, and none of this is veterinary advice.
The long middle of a dog's life. Keeping a healthy weight and an eye on teeth and joints pays off later.
| Size | Young adult | Mature adult | Senior | Geriatric | Typical lifespan |
|---|---|---|---|---|---|
| Small | 1 year | 3 years | 10 years | 14 years | 12 to 16 years |
| MediumYours | 1 year | 3 years | 8 years | 12 years | 10 to 14 years |
| Large | 18 months | 3 years | 7 years | 10 years | 9 to 12 years |
| Giant | 2 years | 3 years | 6 years | 8 years | 7 to 10 years |
These are approximate guides by size, not a veterinary standard. Senior roughly marks the last quarter of a typical lifespan, which is why larger dogs reach it sooner. Your vet’s view of your own dog counts for more.
The size-based chart for every size class, beside the DNA methylation formula and the multiply-by-seven rule. Your dog's size column and closest whole age are marked.
| Dog age | SmallUp to 9 kg | YoursMedium9 to 23 kg | Large23 to 41 kg | GiantOver 41 kg | DNA formulaAny size | × 7 ruleMyth |
|---|---|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 | 31 | 7 |
| 2 years | 24 | 24 | 24 | 24 | 42 | 14 |
| 3 years | 28 | 29 | 30 | 31 | 49 | 21 |
| 4 years | 32 | 34 | 36 | 38 | 53 | 28 |
| 5 yearsClosest | 36 | 39 | 42 | 45 | 57 | 35 |
| 6 years | 40 | 44 | 48 | 52 | 60 | 42 |
| 7 years | 44 | 49 | 54 | 59 | 62 | 49 |
| 8 years | 48 | 54 | 60 | 66 | 64 | 56 |
| 9 years | 52 | 59 | 66 | 73 | 66 | 63 |
| 10 years | 56 | 64 | 72 | 80 | 68 | 70 |
| 11 years | 60 | 69 | 78 | 87 (beyond the typical lifespan) | 69 | 77 |
| 12 years | 64 | 74 | 84 | 94 (beyond the typical lifespan) | 71 | 84 |
| 13 years | 68 | 79 | 90 (beyond the typical lifespan) | 101 (beyond the typical lifespan) | 72 | 91 |
| 14 years | 72 | 84 | 96 (beyond the typical lifespan) | 108 (beyond the typical lifespan) | 73 | 98 |
| 15 years | 76 | 89 (beyond the typical lifespan) | 102 (beyond the typical lifespan) | 115 (beyond the typical lifespan) | 74 | 105 |
| 16 years | 80 | 94 (beyond the typical lifespan) | 108 (beyond the typical lifespan) | 122 (beyond the typical lifespan) | 75 | 112 |
* Past the typical lifespan for that size. The chart keeps adding years at a steady pace, which is how figures above 100 appear, though few dogs of that size reach those ages. DNA formula values are 16 × ln(age) + 31, rounded.
human age = 16 × ln(dog age) + 31
From Wang and colleagues, Cell Systems, 2020. Methylation, a chemical tag on DNA, shifts at predictable places as mammals age. The team read it in just over a hundred Labrador retrievers, matched it against the same regions in humans, and fitted this curve. ln is the natural logarithm.
Fitted on one breed, so smaller and larger dogs may age on a different curve. The logarithm is undefined at zero and falls steeply under a year, crossing zero at about 7.5 weeks, so puppies get a caveat. Past 16 years it goes beyond the study's dogs.
15 for year 1, + 9 for year 2, then + 5 a year (medium)
A widely repeated rule of thumb in the style of veterinary age charts. After year two it adds 4, 5, 6, or 7 human years per dog year for small, medium, large, and giant dogs, because larger dogs age faster and live shorter lives.
An approximation, not a measurement. It is a straight line after year two, it spreads the first year evenly across a puppy's fastest months, and past a size's typical lifespan it keeps climbing beyond 100.
human age = dog age × 7
Usually explained as a rough human lifespan of about 70 divided by a rough dog lifespan of about 10. It lasted because it is easy to remember.
It fails at both ends. Most 1-year-old dogs are near adult size and past puberty, nothing like a 7-year-old child, and a 15-year-old small dog is old but not 105. It also ignores size completely.
The same question for people: an exact age in years, months, and days from a birth date, plus the next birthday.
Count the days since your dog's adoption day, or the weeks until the next vaccination or check-up.
Switch a weight between kilograms and pounds with full precision before you pick a size class.
Dogs grow up far faster than people and then age at a pace that depends on their size, so no fixed ratio can convert dog years to human years. This calculator runs the DNA methylation formula fitted on Labrador retrievers in 2020, a size-based chart that adds 15 human years for the first year, 9 for the second, and 4 to 7 for each year after, and the multiply-by-7 rule for comparison. The arithmetic for each is printed with your dog's numbers in it, so you can see exactly where they agree and where they part ways.
Type years and months, or switch to a birth date and the age is counted to today's date on your device. Years accept decimals, so 2.5 means two and a half years. For a puppy, set years to 0 and enter the months.
Small, medium, large, and giant are listed with their weight ranges in kilograms or pounds. Type an adult weight instead and the class is picked for you. For a puppy, use the weight it is expected to reach, not its weight today.
The DNA methylation formula, the size-based chart, and the multiply-by-7 rule sit side by side with their arithmetic, followed by an approximate life stage for your dog's size and a full chart from 1 to 16 years.
No single conversion exists, so the page shows three and names each one. The spread between them is part of the answer: for a 5-year-old medium dog the size chart says about 39, the DNA formula about 57, and the 7-year rule 35.
Human age = 16 × ln(dog age) + 31, from research on Labrador retrievers. The page says it was fitted on one breed, shows it with a caveat under a year, withholds it below about 7.5 weeks where it turns negative, and flags it as an extrapolation past 16.
Small up to about 9 kg (20 lb), medium to 23 kg (50 lb), large to 41 kg (90 lb), and giant above that. Type an adult weight in either unit and the class follows, with breed examples beside each class.
Puppy, young adult, mature adult, senior, or geriatric, placed on a timeline for your dog's size, with a table showing when each stage begins for every size. Larger dogs reach senior status years earlier than small ones.
Every size class, the DNA formula, and the 7-year rule for each whole year, with your dog's size column and closest age marked. Ages past a size's typical lifespan are flagged rather than presented as normal.
Everything runs in your browser and nothing is uploaded. Every figure is described as an estimate, because breed, size, and health matter more than any formula, and the page is clear that it is not veterinary advice.
No. The 7-year rule is usually explained as a rough human lifespan of about 70 divided by a rough dog lifespan of about 10, and it is wrong at both ends. It makes young dogs far too young: most dogs are close to adult size and past puberty by their first birthday, which is nothing like a 7-year-old child, so both the size chart and the DNA formula give a first year worth about 15 to 31 human years. And it ignores size, so it treats a Chihuahua and a Great Dane as ageing at the same pace when large dogs clearly age faster.
It depends on the method and on size, which is why this page shows more than one answer. By the size-based chart, a 5-year-old medium dog is about 39 and a 5-year-old giant dog about 45. The DNA methylation formula puts any 5-year-old dog at about 57, because it packs most of the ageing into the early years. At 10, the chart gives 56 for a small dog and 80 for a giant one, while the DNA formula gives about 68. Treat the spread as the honest answer: every figure is an estimate, and breed and health matter more than any formula.
It comes from a 2020 study by Wang and colleagues in the journal Cell Systems. As mammals age, chemical tags called methyl groups are added to and removed from DNA at predictable places, and those patterns work as an epigenetic clock. The researchers read them in just over a hundred Labrador retrievers, compared them with the same regions in humans, and fitted human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. A 1-year-old maps to about 31, a 4-year-old to about 53, and a 12-year-old to about 71. It was fitted on one breed, so it may suit very small or very large dogs less well.
Across mammal species, bigger animals usually live longer, but within dogs it runs the other way, and there is no complete explanation yet. Research comparing breeds suggests large dogs age at a faster pace once they are adults, and their very rapid growth as puppies is one of the leading suspects. Growth-related hormones such as IGF-1, which differs strongly between small and large breeds, are among the factors being studied. Whatever the cause, it is why the size chart adds more human years per year for larger dogs, and why they reach senior status sooner.
There is no single birthday. A common approach treats roughly the last quarter of a dog's expected lifespan as its senior years, and because larger dogs have shorter lifespans, they get there sooner. As an approximate guide, this page treats small dogs as seniors from about 10, medium dogs from about 8, large dogs from about 7, and giant dogs from about 6. Your vet's view of your own dog, based on its breed and health, is the better marker.
Enter the age in months with years set to 0, or enter the birth date. Puppies are where the methods disagree most. The size chart spreads the first 15 human years evenly over the first 12 months, so a 6-month-old reads as 7.5, although real development is fastest at the start. The DNA formula gives about 20 at 6 months, but its logarithm falls steeply below a year and reaches zero at about 7.5 weeks, so this page shows it with a caveat under a year and not at all for very young puppies. For large and giant breeds, pick the size from the expected adult weight.
Only general ranges make sense, and individual dogs vary widely. Broadly, small dogs often live around 12 to 16 years, medium dogs around 10 to 14, large dogs around 9 to 12, and giant breeds around 7 to 10. Breed matters within each class, and so do genetics, body weight, and veterinary care, so treat these as rough expectations rather than a prediction for your dog.
Go by the expected adult weight: up to about 9 kg (20 lb) is small, about 9 to 23 kg (20 to 50 lb) is medium, about 23 to 41 kg (50 to 90 lb) is large, and anything heavier is giant. A Chihuahua or Yorkshire Terrier is small, a Cocker Spaniel or Border Collie medium, a Labrador or German Shepherd large, and a Great Dane or Mastiff giant. For a mixed breed, a healthy adult weight is a better guide than guessing the breeds, so type it into the weight field and the class is picked for you.
No. Both real methods here are about dogs: the DNA formula was fitted on Labrador retrievers, and the size classes only make sense for a species whose adults range from a couple of kilograms to well over 50. Cats age on a different curve, and cat breeds vary far less in size, so a cat needs a chart made for cats rather than this one.
No to both. Every figure is an estimate meant to make your dog's age easier to picture, and breed, size, and health matter more than any formula. Questions about your own dog's health, diet, or check-up schedule belong with your vet. The calculator runs entirely in your browser: the age, birth date, and weight you enter are not uploaded, stored, or shared.
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