Reference chart
Dog Years to Human Years Chart
By &Pixels, the studio that builds MyCalculator.to. Figures follow AVMA and AAHA canine life stage guidance, named at the foot of this page.
Four columns, not one, because a Great Dane and a Chihuahua of the same age are years apart in human terms. Find your dog’s adult weight, then read down.
What is a dog year?
A dog year is the human age a dog’s body most closely resembles, and it is not a fixed multiple. Dogs do most of their ageing early: the first year is worth about fifteen human years, the second about nine, and every year after that depends on how big the dog is.
That last part is where the familiar rule falls apart. Multiplying by seven treats a terrier and a mastiff as the same animal on a different scale, when in fact large dogs age faster once they stop growing. By ten, the gap between the smallest and largest bands in this chart is more than twenty human years.
Dog age in human years, by size
| Dog’s age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| Weight | under 20 lb | 21 to 50 | 51 to 100 | over 100 |
| 1 year | 15 | 15 | 14 | 12 |
| 2 years | 24 | 24 | 22 | 20 |
| 3 years | 28 | 29 | 29 | 31 |
| 4 years | 32 | 34 | 35 | 38 |
| 5 years | 36 | 37 | 40 | 45 |
| 6 years | 40 | 42 | 45 | 49 |
| 7 years | 44 | 47 | 50 | 56 |
| 8 years | 48 | 51 | 55 | 64 |
| 9 years | 52 | 56 | 61 | 71 |
| 10 years | 56 | 60 | 66 | 79 |
| 11 years | 60 | 65 | 72 | 86 |
| 12 years | 64 | 69 | 77 | 93 |
| 13 years | 68 | 74 | 82 | 101 |
| 14 years | 72 | 78 | 88 | 108 |
| 15 years | 76 | 83 | 93 | 115 |
| 16 years | 80 | 87 | 99 | 123 |
Notice the first two rows. Every size reaches roughly the same place by two years old, because puppies of all sizes mature at a similar rate. The columns only separate afterwards, and then they separate fast.
The calculators behind this
The four life stages
Vets work in stages rather than birthdays, because the stage is what changes the care. The boundaries move with size, which is the same reason the chart has four columns.
- Puppy. Birth until growth stops, which is 6 to 9 months in a small breed and up to 2 years in a giant one.
- Young adult. From the end of growth to about 3 years. Fully grown, socially still settling.
- Mature adult. From 3 years until the last quarter of the expected lifespan. The longest stage, and the quietest.
- Senior. The last quarter of expected lifespan onward. A giant breed reaches this at 5 or 6; a small one not until 10 or 11.
The senior boundary is the one worth knowing, because it is when twice-yearly checks and baseline bloodwork start being recommended. A giant breed crosses it at five or six. A small one may not cross it until eleven.
To get the number for one specific age rather than read the whole table, the dog age calculator does the lookup and names the life stage. There is a cat age calculator too, and cats work differently enough to be worth its own chart: their ageing does not depend on size at all.
Formula & Methodology
Did you know? Large dogs ageing faster than small ones runs against the usual mammal pattern, where bigger species live longer. Within a species it reverses, and the leading explanation is that fast early growth is paid for later.
Sources
- American Animal Hospital Association, Canine Life Stage Guidelines
- American Veterinary Medical Association, canine life stage and senior care guidance
- Wang et al. 2020, Cell Systems: Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome