How old is your dog in human years?
The idea that one dog year equals seven human years is easy to remember and mostly wrong. Dogs mature very fast — a one-year-old dog is roughly a teenager — and then age at a pace that depends heavily on size: a Great Dane is senior at six or seven, a Chihuahua not until ten or eleven. This dog age calculator converts dog years to human years three ways so you can see the difference: the size-based chart published by the American Veterinary Medical Association (AVMA), the DNA-based formula from a 2020 study, and the old 7× rule.
Enter your dog’s age, or its birth date, and its adult size. You get a human-equivalent age, the life stage your dog is in according to the American Animal Hospital Association (AAHA) guidelines, an interactive chart of all three methods and the full table by size.
It is a fun, informative estimate — not a veterinary assessment. Breed, genetics, weight and care all matter, and your vet is the best guide to your dog’s actual health.
How to use the Dog Age Calculator
- For a puppy, type its age in weeks or pick its birth date: you get the exact weeks and days, the age in months and the usual development band (neonatal, transitional, socialisation window to 12 weeks, juvenile, adolescent). These bands are common breeder and vet-handout conventions, not strict limits.
- Or type your dog’s age in years and choose extra months, or pick a birth date to fill both in.
- Choose the adult size: small (up to 20 lb / 9 kg), medium, large or giant (over 90 lb / 41 kg). For a puppy, choose the size it will be as an adult.
- Read the human-equivalent age from the size chart, then compare the epigenetic formula and the 7× rule underneath.
- Check the life stage and the age at which your dog’s size usually counts as senior.
- Move your pointer or finger across the chart to read all three methods at any age, or use the table below it.
Dog Age Calculator features
Size-aware conversion
Uses the widely published AVMA chart for small, medium, large and giant dogs, interpolated between whole years and extended beyond 16 at the chart’s own rate.
The DNA-based formula
Human age = 16 × ln(dog age) + 31, from epigenetic clocks of Labrador retrievers (Wang et al., Cell Systems, 2020).
Life stage
Puppy, young adult, mature adult or senior, following the AAHA 2019 canine life-stage guidelines.
Interactive chart
Three lines with markers at your dog’s age, a hover read-out and an animated redraw when you change size.
Full table
Dog ages 1–16 for every size class plus the epigenetic value, with your dog’s cell highlighted.
Three ways to count dog years
- Size chart (AVMA). The first year equals about 15 human years for all but giant breeds, the second about 9 more, and after that each year adds roughly 4 (small), 5 (medium), 5–6 (large) or 7 (giant) years. This matches what vets see: bigger dogs age faster and have shorter lives.
- Epigenetic formula. Researchers at UC San Diego compared age-related chemical marks on DNA (methylation) in 104 Labradors with those in humans and found human age ≈ 16 × ln(dog age) + 31. It ages young dogs very quickly — a 1-year-old maps to 31, a 2-year-old to 42 — and then slows. It was derived from one breed, so it does not account for size.
- 7× rule. A rough average from the past, close to the truth only for a medium dog of around 5 to 10 years. It underestimates young dogs and old large dogs.
Worked example
A 5-year-old medium dog (say, a 20 kg border collie): the size chart gives 36 human years; the epigenetic formula gives 16 × ln 5 + 31 = 16 × 1.609 + 31 ≈ 57; the 7× rule gives 35. The dog is a mature adult; a medium dog typically counts as senior from about 9. The same 5-year-old as a giant breed is 45 by the chart and only about two years from senior.
Life stages and what they mean for care
AAHA groups dogs by life stage rather than birthdays: puppy until rapid growth ends (about 6–9 months, longer for big breeds), young adult until physical and social maturity at around 3–4 years, mature adult until the last quarter of expected lifespan, and senior after that. The senior ages shown here use typical lifespans of about 14, 12, 11 and 9 years for small, medium, large and giant dogs — real lifespans vary widely by breed. Senior dogs are usually advised to have check-ups twice a year.
Dog Age Calculator FAQ
Is one dog year really seven human years?
No. A dog’s first year is closer to 15 human years and the second adds about 9. After that the rate depends on size. The dog age calculator shows the 7× figure only for comparison.
Which method is most accurate?
For most dogs the size chart is the most practical, because size strongly affects ageing. The epigenetic formula is based on biology but only on Labradors. Both are estimates.
How do I find my puppy’s age in weeks?
Enter the birth date (or the weeks you know) and read the line under the result: whole weeks plus days, total days and months, counted to today. It is plain date arithmetic, so it is exact if the birth date is. The breed matters only for the human-years estimate, via adult size.
How do I calculate my puppy’s age in human years?
Enter 0 years and the months, and choose the size it will be as an adult. A 6-month-old small or medium puppy is roughly a 7–8-year-old child by the chart; the epigenetic formula puts it nearer 20, because it treats early puppyhood as very fast development.
When is my dog a senior?
Roughly in the last quarter of its expected lifespan — from about 6–7 years for giant breeds to 10–11 for small ones. The calculator shows the typical age for your size.
What size is a mixed-breed dog?
Use its adult weight: up to 20 lb (9 kg) small, 21–50 lb medium, 51–90 lb large, over 90 lb giant. Use the weight converter for kg and lb.
Do you have one for cats?
Yes — the cat age calculator uses the AAHA/AAFP feline life-stage chart. For people, the age calculator gives an exact age.