This dog age calculator converts your dog’s age into human years using a size-adjusted veterinary chart, with the UCSD epigenetic estimate alongside it. Enter an age and an adult size, and you get your dog age in human years, the life stage, and the milestones ahead. It answers how old is my dog in human years for any age from a few weeks to twenty years.
Size matters more than anything else. A 10-year-old Chihuahua is roughly 56 in human years, while a 10-year-old Great Dane is closer to 80. Any conversion that ignores size, including the familiar multiply-by-seven rule, is badly wrong for most dogs.
The full chart below covers every age from 1 to 20 years across four size classes, so you can look your dog up directly.
Dog Years to Human Years Chart
The ages people ask about most, read straight off the dog years chart. Each line gives small, medium, large and giant:
- How old is 1 in dog years: 15 for every size
- How old is 2 in dog years: 24 for every size
- How old is 3 in dog years: 28, 29, 30, 31
- How old is 4 in dog years: 32, 34, 36, 38
- How old is 5 in dog years: 36, 39, 42, 45
- How old is 6 in dog years: 40, 44, 48, 52
- How old is 7 in dog years: 44, 49, 54, 59. The familiar figure of 49 comes from the old multiply-by-seven rule, and it happens to be about right for a medium dog at exactly this age
- How old is 8 in dog years: 48, 54, 60, 66
- How old is 9 in dog years: 52, 59, 66, 73
- How old is 10 in dog years: 56, 64, 72, 80
- How old is 11 in dog years: 60, 69, 78, 87
- How old is 12 in dog years: 64, 74, 84, 94
- How old is 13 in dog years: 68, 79, 90, 101
- How old is 14 in dog years: 72, 84, 96, 108
- How old is 15 in dog years: 76, 89, 102, 115
- How old is 16 in dog years: 80, 94, 108, 122
- How old is 18 in dog years: 88, 104, 120, 136
Asked the other way round, 2 years in dog years is 24, 3 years in dog years is 28 to 31, 5 years in dog years is 36 to 45, 7 years in dog years is 44 to 59, 10 years in dog years is 56 to 80, and 15 years in dog years is 76 to 115. Each range runs from small breeds at the low end to giant breeds at the high end.
The spread widens every year. At age 3 the gap between a small and a giant dog is 3 human years. By age 13 it is 33.
| Dog age | Small (under 20 lb) | Medium (20–50 lb) | Large (50–90 lb) | Giant (over 90 lb) |
|---|---|---|---|---|
| 1 year | 15 | 15 | 15 | 15 |
| 2 years | 24 | 24 | 24 | 24 |
| 3 years | 28 | 29 | 30 | 31 |
| 4 years | 32 | 34 | 36 | 38 |
| 5 years | 36 | 39 | 42 | 45 |
| 6 years | 40 | 44 | 48 | 52 |
| 7 years | 44 | 49 | 54 | 59 |
| 8 years | 48 | 54 | 60 | 66 |
| 9 years | 52 | 59 | 66 | 73 |
| 10 years | 56 | 64 | 72 | 80 |
| 11 years | 60 | 69 | 78 | 87 |
| 12 years | 64 | 74 | 84 | 94 |
| 13 years | 68 | 79 | 90 | 101 |
| 14 years | 72 | 84 | 96 | 108 |
| 15 years | 76 | 89 | 102 | 115 |
| 16 years | 80 | 94 | 108 | 122 |
| 17 years | 84 | 99 | 114 | 129 |
| 18 years | 88 | 104 | 120 | 136 |
| 19 years | 92 | 109 | 126 | 143 |
| 20 years | 96 | 114 | 132 | 150 |
All four sizes share the first two years, because every dog reaches physical and sexual maturity on roughly the same schedule. They diverge from year three, where a small dog gains 4 human years per calendar year and a giant breed gains 7.
How Dog Years Are Calculated
Converting dog to human years, sometimes called canine years, works in three phases, because dogs do not age at a constant rate:
- Year 1 counts as 15 human years. A one-year-old dog is physically an adolescent, sexually mature and close to full height
- Year 2 adds 9 more, bringing a two-year-old to 24. Growth is finished and the dog is a young adult
- Every year after that adds a fixed amount set by adult size: 4 for small, 5 for medium, 6 for large, 7 for giant breeds
So a 6-year-old Labrador, a large dog, is 24 + (4 × 6) = 48 human years.
One dog year is therefore not a single number. During the first year it is worth about 15 human years, during the second about 9, and from year three between 4 and 7 depending on size. Anyone quoting a single conversion factor is averaging away the part that matters.
The front-loading is steep because dogs compress childhood, adolescence and reproductive maturity into roughly 12 months, a stage that takes humans 15 to 18 years.
Why the Multiply-by-Seven Rule Is Wrong
The rule appears to have come from a rough comparison of average lifespans, about 70 human years against 10 dog years, some time in the mid-20th century. It was never based on how dogs develop.
The clearest failure is at the start. A one-year-old dog can reproduce, has a full set of adult teeth and is nearly full size. A seven-year-old child is none of those things, and 15 is the honest comparison.
At the other end it overstates. The rule puts a 15-year-old dog at 105 human years, beyond the human record for most of history, when a 15-year-old small dog is doing something closer to what a 76-year-old person does.
It is right, coincidentally, at around age 10 for a medium dog, where ×7 gives 70 and the chart gives 64. That single coincidence is probably why the rule survived so long.
| Dog age | Old ×7 rule | Chart (medium dog) | Epigenetic formula |
|---|---|---|---|
| 1 year | 7 | 15 | 31 |
| 2 years | 14 | 24 | 42 |
| 5 years | 35 | 39 | 57 |
| 10 years | 70 | 64 | 68 |
| 15 years | 105 | 89 | 74 |
The ×7 rule is wrong at both ends and only roughly right in the middle. It understates a young dog dramatically and overstates an old one.
The UCSD Epigenetic Formula
In 2020, researchers at the University of California San Diego published a conversion based on DNA methylation, the chemical tags that accumulate on DNA as an animal ages. Comparing methylation in 104 Labrador Retrievers against human data gave a logarithmic relationship:
human age = 16 × ln(dog age) + 31
Where ln is the natural logarithm. Since the natural log of 1 is zero, the formula puts a one-year-old dog at exactly 31 human years, and the curve flattens sharply from there:
- 1 year: 31
- 2 years: 42
- 4 years: 53
- 7 years: 62
- 10 years: 68
- 15 years: 74
- 20 years: 79
Read in reverse, human 50 corresponds to a dog of about 3.3 years and human 70 to a dog of about 11.4.
The formula is biologically grounded but has real limits. It came from a single breed, so it accounts for size not at all, and it measures cellular ageing rather than functional life stage. A one-year-old dog behaves like a teenager, not a 31-year-old. Use the chart for practical questions about life stage and the epigenetic number as context, which is why this calculator shows both.
Puppy Age in Human Years
The first year is where the conversion moves fastest, which is why the calculator accepts decimals. Enter 0.5 for a six-month-old puppy.
Eight weeks is the standard minimum age for a puppy to leave its litter, and many jurisdictions set it in law. In human terms that is a toddler of about two and a half, which is a useful frame for how much supervision a new puppy actually needs.
The socialisation window, roughly 3 to 14 weeks, is the period where exposure to people, animals and environments has the most lasting effect on temperament. It closes before most puppies have finished their vaccination series, which is the tension every new owner has to manage.
| Puppy age | Human equivalent | What is happening |
|---|---|---|
| 2 months | about 2.5 years | Weaned, old enough to leave the litter, first vaccinations |
| 3 months | about 4 years | Baby incisors being replaced, socialisation window open |
| 4 months | about 5 years | Permanent teeth coming through, fast growth |
| 6 months | about 7.5 years | Adolescence begins, many breeds near sexual maturity |
| 9 months | about 11 years | Close to adult height, filling out |
| 12 months | 15 years | Physically an adolescent, adult teeth complete |
| 18 months | about 19.5 years | Mentally maturing, giant breeds still growing |
Small breeds mature faster than giant ones. A Chihuahua is essentially full-grown at 9 months, while a Great Dane keeps growing until 18 to 24 months.
How to Tell How Old a Dog Is
If you adopted a dog with no history, teeth are the most reliable single indicator. Up to seven months the permanent set comes in on a known timetable, so an estimate can be accurate to within weeks. Once the full 42 teeth are in, estimates widen to a range of years.
Other signs a vet weighs: cloudiness in the lens of the eye, greying around the muzzle and eyebrows, loss of muscle over the hindquarters, and stiffness on rising. None is decisive alone, and greying varies enormously. Some dogs go grey before three.
For anything that affects care decisions, a vet examination will narrow the estimate far more than any chart can.
| Teeth | Estimated age |
|---|---|
| Baby incisors erupting | 2 to 4 weeks |
| All 28 baby teeth present | 6 to 8 weeks |
| Baby incisors replaced by permanent ones | 3 to 4 months |
| All 42 permanent teeth in, white and clean | 6 to 7 months |
| Permanent teeth, slight dulling, tartar on the rear teeth | 1 to 2 years |
| Tartar on most teeth, visible wear on the incisor tips | 3 to 5 years |
| More wear, some gum recession or discolouration | 5 to 10 years |
| Heavy tartar and wear, teeth possibly missing | 10 years or more |
Teeth give a precise estimate up to about a year, because eruption follows a fixed schedule, and a rough one after that, because wear depends on diet, chewing habits and dental care.
Dog Lifespan by Size
Dogs run against the usual pattern in biology. Across species, larger mammals generally live longer, and an elephant outlives a mouse many times over. Within the dog species the relationship reverses, and a Great Dane may live half as long as a Chihuahua.
The leading explanation is growth rate. Giant breeds reach around 100 times their birth weight in about a year, and that pace of cell division appears to carry a cost in cancer risk and age-related disease. Large breeds do die of cancer at notably higher rates.
Two other factors move the numbers. Mixed-breed dogs of a given size tend to outlive purebreds slightly, and body condition matters a great deal: dogs kept lean live meaningfully longer than overweight dogs of the same breed.
Everything here is an average across populations, and individual dogs vary widely. From the senior threshold onward most vets recommend twice-yearly check-ups, since catching age-related disease early is the largest lever an owner has on both lifespan and quality of life.
| Size | Typical lifespan | Senior from about | Examples |
|---|---|---|---|
| Small, under 20 lb | 12 to 16 years | 11 years | Chihuahua, Dachshund, Toy Poodle |
| Medium, 20 to 50 lb | 10 to 14 years | 10 years | Beagle, Border Collie, Cocker Spaniel |
| Large, 50 to 90 lb | 8 to 12 years | 8 years | Labrador, German Shepherd, Boxer |
| Giant, over 90 lb | 6 to 10 years | 7 years | Great Dane, Mastiff, Irish Wolfhound |
Frequently Asked Questions
How do I convert human years to dog years?
Work the chart backwards. A human age of 24 is a 2-year-old dog of any size, 39 is a 5-year-old medium dog, and 64 is a 10-year-old medium dog. Because the first two years are so front-loaded, human ages below 24 all map inside a dog’s first two years, which is why the reverse conversion is much less precise at the young end.
How many dog years is one human year?
It is not a fixed number, and the answer runs in both directions. One dog year is worth about 15 human years during the first year, about 9 during the second, and between 4 and 7 from year three depending on adult size. So one human year is roughly a fifth of a dog year early on and a quarter of one later. Any single conversion factor averages away the part that matters most.
How old is a 5-year-old dog in human years?
About 36 human years for a small dog, 39 medium, 42 large and 45 for a giant breed. The calculation is 24 for the first two years, plus 4, 5, 6 or 7 for each year after depending on size.
How old is 7 in dog years?
Roughly 44 human years for a small dog, 49 medium, 54 large and 59 for a giant breed. The familiar 49 comes from the multiply-by-seven rule, which happens to be about right for a medium dog at this age and wrong at most others.
How old is 10 in dog years?
About 56 human years for a small dog, 64 medium, 72 large and 80 for a giant breed. Age 10 is also where the old ×7 rule coincidentally lines up with the chart for a medium dog, giving 70 against 64.
How old is 13 in dog years?
About 68 human years for a small dog, 79 medium, 90 large and 101 for a giant breed. Most large and giant dogs are well into old age by 13, while small breeds often have several years ahead of them.
Is one dog year really seven human years?
No. The rule understates young dogs badly and overstates old ones. A one-year-old dog is sexually mature with a full set of adult teeth, which is nothing like a seven-year-old child. It also ignores size, the strongest predictor of canine ageing.
How can I tell how old my dog is?
Teeth are the best single guide. All 28 baby teeth means 6 to 8 weeks, a clean full set of 42 permanent teeth means about 6 to 7 months, and tartar with visible wear on the incisors suggests 3 to 5 years. After the permanent set is in, estimates widen to a range of years, so a vet exam will narrow it considerably.
What is the epigenetic dog age formula?
Human age = 16 × ln(dog age) + 31, published by UC San Diego in 2020 from DNA methylation data in Labradors. It maps a one-year-old dog to 31 human years and a ten-year-old to about 68. It reflects cellular ageing rather than behaviour or life stage, so treat it as a complement to the veterinary chart.
Why do small dogs live longer than large dogs?
The most likely reason is growth rate. Giant breeds reach around 100 times their birth weight within a year, and that pace appears to carry a cost in cancer risk and age-related disease. It reverses the usual pattern across species, where larger animals generally live longer.
When is a dog considered a senior?
It depends on size: around 11 years for small dogs, 10 for medium, 8 for large and 7 for giant breeds. Most vets recommend twice-yearly check-ups from that point, along with bloodwork to catch kidney, liver and thyroid changes early.