Convert dog years to human years by breed size, three ways
| Dog Age | Small (<20 lb) | Medium (21-50 lb) | Large (51-100 lb) | Giant (>100 lb) |
|---|---|---|---|---|
| 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 |
The size-based chart used by the AKC and veterinary schools: year one ≈ 15, year two brings the total to 24, and after that smaller dogs add roughly 4 human years per year while giant breeds add 6-8. The calculator interpolates between rows for fractional ages.
| Size | Typical Lifespan | Senior From | Twice-Yearly Vet Visits |
|---|---|---|---|
| Small (<20 lb) | 10-16 years | ~7 | Recommended from senior status |
| Medium (21-50 lb) | 10-14 years | ~7 | Recommended from senior status |
| Large (51-100 lb) | 8-12 years | ~6 | Recommended from senior status |
| Giant (>100 lb) | 6-10 years | ~5 | Recommended from senior status |
Lifespan bands are typical published ranges (breed-club and veterinary sources; the Great Dane Club of America lists 7-10 years for that breed). Senior thresholds follow AVMA guidance: small dogs and cats around 7, large breeds 5-6. Research note: a University of Göttingen analysis found each 4.4 lb of body mass trims roughly a month off life expectancy.
Three conversions run side by side, because "dog years" has three competing answers and the honest move is to show them all.
AKC size chart: year one = 15, year two = 24 total, then +4 to +8 per year depending on size class, following the published chart table (interpolated for fractional ages). The 7-year rule: age × 7, the folk formula, kept for comparison. The epigenetic clock: human age = 16 × ln(dog age) + 31, derived in a 2020 UC San Diego study that sequenced DNA from 104 Labrador Retrievers and matched methylation patterns against human aging.
Pick your dog's adult weight class — use their lean adult weight, not current weight — and enter an age or a date of birth. The date input computes exact age, so a dog born March 15, 2019 shows 7.46 years in late August 2026, not a rounded 7. Rescue dog with unknown birthday? Use your best estimate; a vet's dental-age read is usually within a year for adults.
Take a 7-year-old, 70-pound Golden Retriever. The AKC chart (large column) says 50 human years. The 7-year rule says 49 — almost identical, because the two methods cross right around age 7 for large dogs, one of the few places the old rule works. The epigenetic clock says 16 × ln(7) + 31 = 62, notably older, because logarithmic aging front-loads the early years. Life stage: large dogs are seniors from ~6, so this dog is a senior — twice-yearly checkups and senior bloodwork are the standard recommendation. For contrast, a 7-year-old Chihuahua (small) charts at 44 and is barely into senior status, with half its expected lifespan still ahead.
Use the AVMA guideline: the first year of a medium dog's life equals about 15 human years, the second adds 9 more (24 total), and each year after that adds about 4-6 human years depending on breed size. The old multiply-by-7 rule understates the first two years and overstates everything after.
No. Dogs mature much faster than that early and slower later. A 1-year-old dog is closer to a 15-year-old human (or 31 by the epigenetic clock), while a 10-year-old small dog is around 56-60, not 70. The 7:1 rule likely started as a marketing shorthand in the mid-20th century to get owners into the vet once a year.
A 2020 UC San Diego study of 104 Labrador Retrievers derived human age = 16 × ln(dog age) + 31, using DNA methylation patterns shared between dogs and humans. It's the most science-backed conversion, but it was calibrated on one breed, so it fits Labradors best and approximates others.
It's the exception to the mammal rule, and it isn't fully explained. Research from the University of Göttingen found every 4.4 pounds of body mass cuts roughly a month off a dog's life expectancy, likely because large dogs age faster at the cellular level and develop age-related diseases, including cancer, sooner. Small breeds routinely live into their mid-teens; giant breeds often don't see 10.
Roughly age 7 for small and medium dogs, 5 to 6 for large breeds, per the AVMA. Giant breeds hit senior status youngest. Senior status matters practically: it's when vets recommend twice-yearly checkups and senior bloodwork panels.
Typical published ranges: small breeds (under 20 lb) 10-16 years, medium (21-50 lb) 10-14, large (51-100 lb) 8-12, and giant (over 100 lb) 6-10. Individual breeds vary inside those bands; the Great Dane Club of America, for example, lists 7-10 years.