What is my dog’s age in human years?
It depends on size as much as age. Here’s your dog’s answer.
- In human years
- 36
A Golden Retriever aged 5 years is about 36 in human years.
- Age
- 5 years
- DNA method2020 study, shown for comparison
- 57
- Size group
- Large (51 to 100 lb)
- Typical life span
- 10 to 12 years
- Next birthday
- October 5, 2027
- Days to next birthday
- 365
- In human years at the next birthday
- 45
Answer for the example date Monday, October 5, 2026. It changes to today's date when the page loads.
In human years: 36. A Golden Retriever aged 5 years is about 36 in human years.
How old is that in human years?
How to calculate
Converts a dog’s age to human years with the size-based chart vets use, and shows the 2020 DNA-method estimate for comparison.
Example with the default inputs (What breed? Golden Retriever, What do you know? Birthday, When were they born? October 5, 2021, Age on October 5, 2026) on the example date Monday, October 5, 2026: A Golden Retriever aged 5 years is about 36 in human years.
Method: Read the human age for the dog’s age and size group off the size chart, on a straight line between whole years; the DNA method is 16 ln(age) + 31.
- The size group comes from the breed’s adult weight: small up to 20 lb, medium 21 to 50 lb, large 51 to 100 lb, giant over 100 lb.
- Between whole years, the chart is read on a straight line; year 0 counts as 0 human years, and past 16 the chart’s last yearly step repeats.
- Age from a birthday is days ÷ 365.2425 years; the displayed age is the calendar difference in whole years, months, and days.
- The DNA method comes from a study of Labrador Retrievers and is shown for comparison only; it is left out for puppies under about 7 weeks, where it would be below 0.
- A February 29 birthday falls on February 28 in other years.
Worked examples
Each example is checked against the calculator on every build.
- What breed? Golden Retriever, What do you know? Age, Years 5, Months 0 gives In human years 36, DNA method 56.751007, Size group Large (51 to 100 lb), Typical life span 10 to 12 years.Source: Wang et al., 2020
- What breed? Great Dane, What do you know? Age, Years 6, Months 6 gives In human years 52.5, DNA method 60.948835.
- What breed? Chihuahua, What do you know? Birthday, When were they born? 2020-02-29, Age on 2026-09-27 gives Age 6 years, 6 months, 29 days, In human years 42.305811, Next birthday 2027-02-28, Days to next birthday 154, In human years at the next birthday 44.
- What breed? Golden Retriever, What do you know? Birthday, When were they born? 2026-09-07, Age on 2026-09-28 gives Age 21 days, In human years 0.862441.
How it works
1. Size group. The breed sets the size group, from its adult weight on the American Kennel Club breed page:
| Size group | Adult weight |
|---|---|
| Small | up to 20 lb |
| Medium | 21 to 50 lb |
| Large | 51 to 100 lb |
| Giant | over 100 lb |
When a breed's weight range crosses a limit, the middle of the range decides. Mixed breeds pick the size directly.
2. Age in years. The age shown is the calendar difference from the birthday to the age-on date in whole years, months, and days (for example 21 days, or 6 years, 6 months, 29 days); parts that are 0 are left out. For the chart, with a birthday, the age is the number of days from the birthday to the age-on date (today, unless you change it), divided by 365.2425, the average length of a year. With years and months (or when the birthday is left empty), it is years + months ÷ 12.
3. Human years (size chart). Look up the dog's size group in the chart below. Between two whole years, go the same share of the way from one row to the next (a straight line). Before the first birthday, go from 0 at birth to the year-1 value. After 16, keep adding the chart's last yearly step (4, 4, 6 and 7 human years for small, medium, large and giant).
4. DNA method. human age = 16 × ln(dog age in years) + 31, from Wang et al. (2020). It is shown for comparison only.
| Dog age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 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 |
Assumptions
- The chart gives whole years only; the straight line between them is this calculator's choice.
- The next birthday is the first birthday after the age-on date. A February 29 birthday falls on February 28 in other years.
- A birthday after the age-on date gives no answer.
Worked examples by hand
A Golden Retriever born September 7, 2026, on September 28, 2026. The age is 21 days. That is 21 ÷ 365.2425 = 0.0575 years, so on the chart (0 at birth to 15 at year 1 for a large dog) the dog is 0.0575 × 15 = 0.86 human years, shown as 1. The DNA method gives no value below about 7 weeks.
A 5-year-old Golden Retriever. Golden Retrievers weigh 55 to 75 lb, so the size is large. The chart gives 36 human years at 5. The DNA method gives 16 × ln 5 + 31 = 16 × 1.6094 + 31 = 56.75.
A Great Dane aged 6 years 6 months. Great Danes weigh 110 to 175 lb, so the size is giant. The chart gives 49 at 6 and 56 at 7. Halfway between is 49 + 0.5 × 7 = 52.5. The DNA method gives 16 × ln 6.5 + 31 = 60.95.
A Chihuahua born February 29, 2020, on September 27, 2026. Chihuahuas weigh up to 6 lb, so the size is small. From February 29, 2020 to September 27, 2026 is 2,402 days, or 2,402 ÷ 365.2425 = 6.5765 years (shown as 6 years, 6 months, 29 days: February 29, 2020 plus 78 months is August 29, 2026, and 29 days more reach September 27). The chart gives 40 at 6 and 44 at 7, so the dog is 40 + 0.5765 × 4 = 42.31 human years. The next birthday is February 28, 2027 (2027 is not a leap year), 154 days later, when the dog turns 7: 44 on the chart.
Other questions people ask
What's the difference between the size chart and the DNA method?
**The size chart** is the conversion chart used by veterinarians. It accounts for the fact that different sized dogs age at different rates: larger dogs age faster than smaller ones. It's the most practical and widely accepted method, and it is the main answer on this page. **The DNA method** uses the formula 16 × ln(dog's age) + 31, based on DNA methylation patterns (Wang et al., Cell Systems, 2020). This research from UC San Diego shows how molecular aging markers change in both humans and dogs. However, the formula was developed from Labrador Retrievers, so it may not be as accurate for all breeds. **Key difference:** The size chart is practical and breed-appropriate, while the DNA method represents newer aging science but has limitations in universal application.
Why do different sized dogs age at different rates?
This is known as the “size-longevity paradox” in canine biology. While larger animals typically live longer across different species, the opposite is true within the dog species. Small dogs consistently outlive their larger counterparts. **Scientific explanation:** Large dogs experience “accelerated aging”: their entire life “unwinds in fast motion.” Research shows that for every 2 kg (4.4 pounds) of additional body mass, a dog's life expectancy is reduced by about one month. **Source:** Kraus, Pavard and Promislow, The size–life span trade-off decomposed: why large dogs die young, The American Naturalist, 2013.
Is the old 7-year rule accurate?
**No.** Multiplying a dog's age by 7 is too simple, and its origin is unclear. **Why it's wrong:** - It's linear, but canine development is highly non-linear - A 1-year-old dog is not equivalent to a 7-year-old child: it's more like a 15-year-old adolescent - It completely ignores breed and size differences - It doesn't account for the fact that dogs mature rapidly in their first 2 years Size-based charts, like the one on this page, have replaced it.
How accurate is the DNA method?
The formula (16 × ln(dog's age) + 31) comes from a 2020 study by researchers at UC San Diego, published in Cell Systems. **Scientific basis:** The formula is based on DNA methylation patterns that change predictably as both humans and dogs age. It uses the natural logarithm to capture the rapid initial aging of dogs followed by a slowing rate in later years. **Limitations:** The study was based on 104 Labrador Retrievers. Because different breeds have widely varying lifespans, the formula's accuracy for other breeds is untested. For very young puppies (under about 7 weeks) the formula gives a number below zero, so this page does not show it. **Source:** Wang et al., Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome, Cell Systems, 2020.
Why do some breeds have shorter lifespans than others?
**Size:** As mentioned above, larger breeds age faster. **Face shape:** Flat-faced (brachycephalic) breeds often have breathing problems, and large studies of UK dogs have found shorter lives on average in several of these breeds. **Genetic factors:** Some breeds have genetic predispositions to certain health conditions that affect longevity. The typical life span shown for each breed comes from the American Kennel Club.
How do veterinarians use these age calculations?
Veterinarians use a dog's life stage to plan care and health screenings. **Life stages:** The American Animal Hospital Association (AAHA) defines the stages puppy, young adult, mature adult, senior, and end of life. A dog is a senior in roughly the last quarter of its expected life span, so large breeds become seniors earlier than small ones. **Clinical applications:** Age-appropriate vaccinations, dental care, nutrition, exercise recommendations, and screening for age-related conditions like arthritis, cancer, and cognitive decline. **Source:** 2019 AAHA Canine Life Stage Guidelines.
Can I use this calculator for mixed-breed dogs?
Yes. Pick one of the mixed-breed options at the top of the breed list. Each matches a size group by adult weight: small (up to 20 lb), medium (21 to 50 lb), large (51 to 100 lb), or giant (over 100 lb).
What factors can affect my dog's actual lifespan?
**Neutering status:** Research indicates that neutered dogs, on average, live longer than their intact counterparts. **Body condition:** Maintaining a healthy weight is strongly linked to longevity. A study on Labrador Retrievers found that dogs kept at a healthy weight lived, on average, about two years longer than overweight peers. **Other factors:** Quality of veterinary care, nutrition, exercise, genetics, and environmental factors all play significant roles in determining actual lifespan. **Important note:** The calculations in this calculator provide estimates based on breed averages. Individual dogs may vary significantly from these averages.
How often should I recalculate my dog's age?
**Annual updates:** It's a good idea to recalculate your dog's age at least once per year, ideally around their birthday. **Life stage transitions:** Pay special attention when your dog transitions between life stages (puppy to adult, adult to senior), as this may affect their care needs. **Health changes:** If your dog experiences significant health changes or weight changes, recalculating can help you understand their current life stage and appropriate care requirements.