Dog Age Calculator
Your dog's real age and life stage come first; the "human years" figures are rough comparisons, not veterinary measurements. Two methods are shown because they disagree — there is no single conversion.
Before you start
Method : actual age and AAHA life stage first; two labelled human-years comparisons (size rule of thumb and a Labrador-only DNA study).
Checked : arithmetic tested against the worked examples; sources checked 5 October 2026. Not a veterinary assessment.
Review : not reviewed by a veterinarian.
Your entries stay in this browser tab; nothing is sent or stored.
Enter age and adult weight to see life stage and human-years comparisons.
| Dog age | toy | small | medium | large | giant | Lab DNA |
|---|---|---|---|---|---|---|
| 1 y | 15 | 15 | 15 | 15 | 15 | 31 |
| 2 y | 24 | 24 | 24 | 24 | 24 | 42 |
| 5 y | 36 | 38 | 39 | 42 | 45 | 57 |
| 8 y | 48 | 51 | 54 | 60 | 66 | 64 |
| 10 y | 56 | 60 | 64 | 72 | 80 | 68 |
| 12 y | 64 | 69 | 74 | 84 | 94 | 71 |
| 15 y | 76 | 83 | 89 | 102 | 115 | 74 |
How to Use This Calculator
- Enter a birth date, or the known/estimated age
- Enter the adult weight in lb or kg
- Press Calculate
Methodology & assumptions
Actual age is completed calendar months from birth to your local today (or the age you enter). Size band comes from adult weight: toy <10 lb, small 10–24.9, medium 25–49.9, large 50–89.9, giant ≥90 lb (1 kg = 2.20462 lb).
Size chart (rule of thumb): 15 human-years for year one, +9 for year two (the AVMA breakdown quoted by the AKC), then +4 / 4.5 / 5 / 6 / 7 per year for toy → giant. The AKC gives about 5 a year for a medium dog; the other factors are this site's convention.
DNA-methylation formula (Wang et al. 2020): human age = 16 × ln(dog age in years) + 31, fitted on 104 Labrador retrievers aged up to 16. Shown only for ages 1–16 years; it is not validated for other breeds.
Life stage (AAHA 2019): puppy until rapid growth stops (site uses 6 months toy/small, 9 medium, 12 large/giant), young adult to 3 years, mature adult until the last 25% of estimated lifespan, then senior. Estimated lifespan is a broad size range (toy 12–16, small 12–15, medium 10–14, large 9–12, giant 7–10 years — site convention informed by the AKC and UK VetCompass studies); senior starts at 75% of the range midpoint.
Worked examples
Medium (40 lb), 5 y 0 m: chart 24 + 3 × 5 = 39; methylation 16 × ln 5 + 31 = 56.8; stage mature adult (senior from 9 y 0 m).
Giant (50 kg = 110.2 lb), 7 y 0 m: chart 24 + 5 × 7 = 59; methylation 62.1; stage senior (from 6 y 5 m).
Toy (8 lb), 4 months: chart 5 human-years; methylation not shown (under 1 year); stage puppy.
Understanding your result
The two human-year figures can differ by 15+ years for the same dog — that gap is the honest uncertainty. Use the life stage to talk with your vet about age-appropriate checks; breed, genetics, body condition and disease matter more than any chart.
Sources & further reading
- How to Calculate Dog Years to Human Years — American Kennel ClubQuotes the AVMA 15 / +9 / ~5-per-year breakdown for a medium dog. Checked 5 October 2026.
- Wang T et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems 2020;11(2):176–185.e6Source of 16 ln(age) + 31; Labrador retrievers only.
- Creevy KE et al. 2019 AAHA Canine Life Stage Guidelines. JAAHA 2019;55(6):267–290Puppy / young adult / mature adult / senior (last 25% of estimated lifespan) / end of life.
- McMillan KM et al. Longevity of companion dog breeds: those at risk from early death. Scientific Reports 2024;14UK breed lifespans; smaller breeds generally longer-lived.
- O'Neill DG et al. Longevity and mortality of owned dogs in England. The Veterinary Journal 2013;198(3):638–643
Frequently Asked Questions
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