AAHA Dog Age by Size Class - Open Human-Years Table and Cat Companion Chart

Download the size-adjusted dog age open table (small to giant) plus cat human-years CSV. Citeable methodology, senior thresholds, free downloads.

Rajkishor Sahu
By Rajkishor Sahu Software Engineer, Founder of Daily Calcs
· Published October 15, 2026 · 7 min read

Size-Adjusted Dog Age As Open Data

A 1-year-old dog is about 15 human years and a 2-year-old about 24 — then size splits the curve: roughly +4 / +5 / +6 / +7 human years per dog year for small / medium / large / giant. This page packages that chart as downloadable CSVs with senior-start ages and a cat companion table so rescues and journalists can cite one URL.

Last reviewed: · Sources: AAHA canine life stage materials & age poster; AVMA senior-pet guidance; International Cat Care

Editorial note: Human-year conversion is a planning aid, not a diagnosis. Use the Dog Age Calculator by Birth Date for exact ages from a birth date.

Research method: Tables are generated from the same dogToHumanAge / catToHumanAge engines as our public calculators. Senior thresholds match the birth-date calculator size config.

Pet age open tables · Snapshot verified

Size-adjusted dog aging: year 1 ≈ 15 human years, year 2 ≈ 24, then about +4 / +5 / +6 / +7 per year for small / medium / large / giant breeds. At age 10, a giant dog is about 24 human years older than a small dog on this chart. Cats share the first two years, then add +4 each year.

small senior starts
10 years
+4/yr after age 2
medium senior starts
9 years
+5/yr after age 2
large senior starts
8 years
+6/yr after age 2
giant senior starts
6 years
+7/yr after age 2

Chart adapted from the Dog Owner's Home Veterinary Handbook size table (also shown on AAHA's canine/feline age poster). Cat curve follows International Cat Care. Educational planning only — AAHA prefers life stages over human-age math for clinical care. Downloads: dog by size CSV · size meta CSV · cat human-years CSV.

Highlight years from the full 16-year dog table (download CSV for every year). Values are human-year equivalents by size class.
Dog age Small Medium Large Giant 7× rule
1 yr 15 15 15 15 7
2 yr 24 24 24 24 14
5 yr 36 39 42 45 35
8 yr 48 54 60 66 56
10 yr 56 64 72 80 70
12 yr 64 74 84 94 84
15 yr 76 89 102 115 105
Cat age → human years (years 1–12 shown; CSV covers 1– 20).
Cat age Human years Life stage
1 yr 15 Junior
2 yr 24 Adult
3 yr 28 Adult
4 yr 32 Adult
5 yr 36 Adult
6 yr 40 Mature
7 yr 44 Mature
8 yr 48 Mature
9 yr 52 Mature
10 yr 56 Senior
11 yr 60 Senior
12 yr 64 Senior

What The Data Shows

The 7× rule fails early and late

At age 1 the 7× rule says 7; the size chart says 15. At age 10 a small dog is about 56 human years while the 7× rule says 70 — and a giant is about 80.

Size gap compounds after year 2

By age 10 the giant-vs-small gap is about 24 human years on this chart. That is why senior wellness timing must be size-aware.

Cats stay on a single adult rate

After year 2, cats add about +4 per year — the same adult rate as small dogs — while large and giant dogs pull ahead.

Method And Limits

  1. Dog years 1-16: dogToHumanAge from Daily Calcs (year 1 ≈ 15, year 2 ≈ 24, then size rates 4/5/6/7).
  2. Senior starts: small 10, medium 9, large 8, giant 6 (birth-date calculator config).
  3. Cat years 1-20: ICatCare-style curve via catToHumanAge + getCatLifeStage.
  4. Not clinical AAHA formulas: educational packaging of a published size chart.
  5. Refresh: pnpm pets:open-data.

For narrative deep-dives, see How Old Is My Dog in Human Years and When Is a Dog Considered Senior.

Official And Supporting Sources

Next Step

Download the dog size CSV, then run your pet’s birth date through the Dog Age Calculator by Birth Date or Cat Age Calculator by Birth Date.

Frequently Asked Questions

What is the AAHA dog age by size open table?

It is a downloadable, citeable conversion of whole dog years into human-year equivalents for four size classes — small, medium, large, and giant — using the widely published multi-stage chart adapted from the Dog Owner’s Home Veterinary Handbook and shown on AAHA’s canine/feline age poster. Year 1 maps to about 15 human years, year 2 to about 24, then roughly +4, +5, +6, or +7 human years per dog year by size.

Is this an official AAHA clinical formula?

No. AAHA publishes life-stage guidelines and an age poster for education. AAHA prefers life stages over human-age math for clinical care. Daily Calcs publishes the same size-adjusted chart used in our calculators so journalists, rescues, and breed clubs can cite one transparent table with a verified date and CSV.

At what age is a dog considered senior on this table?

Senior screening thresholds in our open meta CSV are 10 years for small, 9 for medium, 8 for large, and 6 for giant — matching our birth-date calculator. Exact senior labeling still depends on breed, health, and your veterinarian.

Where can I download the CSVs?

Dog human-years by size: /data/reports/aaha-dog-age-by-size-class-2026.csv. Size meta (aging rates, senior starts, expectancy): /data/reports/aaha-dog-size-class-meta-2026.csv. Cat companion table: /data/reports/icatcare-cat-age-human-years-2026.csv. Regenerate with pnpm pets:open-data.

How do cats compare on this page?

Cats share the first two years with dogs (~15 at year 1, ~24 at year 2), then add about +4 human years per cat year — the International Cat Care style curve used in our cat calculators. The cat CSV also includes life-stage labels.

Can I republish or cite this table?

Yes. Use the citation block on this page. Credit the Dog Owner’s Handbook / AAHA age-poster chart for dogs, International Cat Care for cats, and Daily Calcs for the packaged CSV and methodology. Link back to this URL.

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