How old is my dog in human years?

Using the UC San Diego scientific formula (Human Age = 16 × ln(dog age) + 31), a 1-year-old dog is approximately 31 human years, a 5-year-old dog is approximately 57 human years, and a 10-year-old dog is approximately 68 human years for a medium-sized breed. This varies by breed size — large and giant breeds age faster than small breeds. The old multiply-by-7 rule is scientifically inaccurate.

Is the 7-year rule for dogs accurate?

No — the multiply-by-7 rule is a myth with no scientific basis. In 2020, UC San Diego researchers used DNA methylation mapping to develop the accurate formula: Human Age = 16 × ln(dog age) + 31. Dogs age extremely rapidly in early life and much more slowly in later years. The ×7 rule significantly underestimates age in early years and produces inaccurate results throughout a dog's life.

How old is a 7-year-old dog in human years?

Using the scientific formula, a 7-year-old medium-sized dog is approximately 69 human years — not 49 as the ×7 rule suggests. For small breeds it's around 63 human years; large breeds around 74 human years; giant breeds around 80 human years. A 7-year-old dog is firmly in the senior life stage for most medium and large breeds.

How old is my cat in human years?

Cats age rapidly in their first two years: a 1-year-old cat equals approximately 15 human years, and a 2-year-old cat equals about 24 human years. After age 2, cats age roughly 4 human years per cat year. A 5-year-old cat is approximately 36 human years; a 10-year-old cat is approximately 56 human years; a 15-year-old cat is approximately 76 human years.

When is a dog considered a senior?

It depends on breed size. Small breeds (under 20 lbs) become senior at 10–12 years. Medium breeds at 8–10 years. Large breeds at 7–8 years. Giant breeds at just 5–6 years. In human-year equivalents, dogs enter their senior phase at around 60–65 human years — which arrives much sooner for large and giant breeds.

When is a cat considered a senior?

Cats are generally considered senior at 10–12 years old (approximately 56–64 human years equivalent) and geriatric at 15+ years (approximately 76+ human years equivalent). Indoor cats typically live 13–17 years; outdoor cats average 10–12 years.

How old is a 10-year-old dog in human years?

A 10-year-old dog is approximately 70–90 human years depending on breed size: small breeds ≈ 70 human years, medium breeds ≈ 77 human years, large breeds ≈ 83 human years, giant breeds ≈ 90 human years. All size categories are firmly in the senior or geriatric life stage at age 10.

HomePet Age Calculator

🎂 Free Scientific Age Calculator

How Old Is My Dog or Cat in Human Years? (2026 Scientific Formula)

Last updated: June 2026

The old "multiply by 7" rule is wrong. Scientists at UC San Diego developed a DNA-based formula that accurately maps dog aging to human aging. Use it free below.

⚠️ The '×7 Rule' Is a Myth: A 1-year-old dog is NOT equivalent to a 7-year-old human. Using DNA methylation research, scientists at UC San Diego found a 1-year-old dog is equivalent to approximately 31 human years. Dogs age extremely fast early in life, then slow down significantly — the relationship is logarithmic, not linear.

✅ UC San Diego Scientific Formula✅ Breed Size Adjusted✅ Dog & Cat✅ Life Stage Breakdown✅ Free

Step 1 — Pet Type

Step 2 — Pet's AgeMy pet is under 1 year old

Age in years (1–25)

Complete Dog & Cat Age Conversion Chart (2026)

Pre-calculated human-year equivalents using the scientific formulas above.

🐶 Dog Age → Human Years (by breed size)

Dog Age	Small (<20lb)	Medium (20–50lb)	Large (50–90lb)	Giant (90lb+)
6 months	22	23	25	27
1 year	29	31	33	36
2 years	40	42	46	49
3 years	47	51	55	59
4 years	52	57	62	66
5 years	56	62	67	72
6 years	60	66	71	76
7 years	63	69	74	80
8 years	66	72	77	83
9 years	68	74	80	87
10 years	70	77	83	90
11 years	72	79	85	92
12 years	74	81	87	95
13 years	75	82	89	97
14 years	77	84	91	99
15 years	79	86	92	99

🐱 Cat Age → Human Years (AAHA guidelines)

Cat Age	Human Equivalent	Life Stage
6 months	10 years	Kitten
1 year	15 years	Junior
2 years	24 years	Young Adult
3 years	28 years	Prime
4 years	32 years	Prime
5 years	36 years	Prime
6 years	40 years	Mature
7 years	44 years	Mature
8 years	48 years	Mature
9 years	52 years	Mature
10 years	56 years	Senior
11 years	60 years	Senior
12 years	64 years	Senior
13 years	68 years	Senior
14 years	72 years	Senior
15 years	76 years	Geriatric
16 years	80 years	Geriatric
18 years	88 years	Geriatric
20 years	96 years	Geriatric

Frequently Asked Questions

The science of pet aging, explained.

How Dog Years Really Work: Beyond the ×7 Myth

The old rule that "one dog year equals seven human years" is a myth that significantly overestimates your dog's age in human terms, especially for young dogs and large breeds. The UC San Diego scientific formula, published in 2020, uses DNA methylation patterns to map dog aging to human aging. The result: dogs age much faster in their first two years (reaching human-equivalent age 40 by age 2), then aging slows dramatically. A 1-year-old dog is roughly 31 in human years, not 7.

Our calculator above uses this scientific formula, adjusted for breed size. Small breeds(under 20 lbs) age more slowly after maturity and can live 15–18 years. Medium breeds(20–50 lbs) typically live 12–15 years. Large breeds (50–90 lbs) live 10–12 years, andgiant breeds (over 90 lbs) often only live 8–10 years. This means a 7-year-old Great Dane is a senior citizen, while a 7-year-old Chihuahua is middle-aged.

Cat Age Conversion: How Old Is Your Cat?

Cats age differently from dogs. The first year of a cat's life equals about 15 human years, the second year adds 9 more (making a 2-year-old cat 24 in human years), and each subsequent year adds roughly 4 human years. So a 10-year-old cat is approximately 56 in human years, and a 15-year-old cat is about 76. Indoor cats typically live 15–20 years, while outdoor cats average only 4–5 years due to accidents, disease, and predators.

Cats are considered senior at age 11 and geriatric at age 15. Senior cats need more frequent vet checkups (every 6 months), bloodwork to monitor kidney and thyroid function, and adjustments to diet and activity. See our senior pet care costs guide for what to expect.

Why Knowing Your Pet's Age in Human Years Matters

Understanding your pet's human-equivalent age helps you:

Schedule appropriate vet visits: Senior pets need twice-yearly checkups, not annual ones
Watch for age-related conditions: Arthritis, dental disease, and cognitive decline appear at different ages by breed size
Adjust diet: Senior formulas have fewer calories and more joint support ingredients
Plan for increased costs: Senior pets typically cost 2–3x more in veterinary care — see our lifetime cost calculator
Consider pet insurance timing: Insurance is much cheaper when purchased young — see insurance for senior dogs

Use our calculator above to find your pet's human-equivalent age, then plan accordingly for their life stage. Early intervention for age-related conditions can add years to your pet's life and save thousands in veterinary costs.

📍 Vet Costs by City

See average pet care costs and local vet clinics in cities across the US.

Bakersfield, CA

$300–$600/yr · 65 clinics

El Paso, TX

$750–$1400/yr · 70 clinics

Boise, ID

$800–$1500/yr · 45 clinics

San Diego, CA

$1200–$2500/yr · 180 clinics

Knoxville, TN

$750–$1400/yr · 55 clinics

Albuquerque, NM

$780–$1450/yr · 65 clinics

Omaha, NE

$800–$1600/yr · 95 clinics