Convert Dog Years to Human Years: How old is your dog really?

“1 dog year = 7 human years” is a myth. Dogs mature much faster in the first two years and then age at different speeds depending on size and weight. Below you’ll find the best rules of thumb, a practical chart, life stages, health tips—and how to add healthy years to your dog’s life.

Contents

• Why the 7-year rule is wrong
• Quick calculator: dog years to human years
• Age by weight class
• Life stages by size
• Staying healthy: checkups & prevention
• Frequently asked questions (FAQ)

Why the 7-year rule is wrong

In the first year a puppy becomes (almost) an adult—that’s roughly 15 human years. In the second year you can add about 9 human years. After that, aging slows and depends on size, weight, genetics, diet, and activity: small dogs typically live longer than large and giant breeds.

Quick calculator (rule of thumb)

• Year 1 = 15 human years
• Year 2 = +9 → total 24
• from year 3, add per dog year:
  • Small (<10 kg / <22 lb): +4 human years/year
  • Medium (10–25 kg / 22–55 lb): +5
  • Large (25–45 kg / 55–100 lb): +6
  • Giant (>45 kg / >100 lb): +7

Note: These are approximations. Individual breeds can differ.

Dog years to human years by weight class

Dog years	Small (<10 kg / <22 lb)	Medium (10–25 kg / 22–55 lb)	Large (25–45 kg / 55–100 lb)	Giant (>45 kg / >100 lb)
1	15	15	15	15
2	24	24	24	24
3	28	29	30	31
4	32	34	36	38
5	36	39	42	45
6	40	44	48	52
7	44	49	54	59
8	48	54	60	66
9	52	59	66	73
10	56	64	72	80
11	60	69	78	87
12	64	74	84	94
13	68	79	90	101
14	72	84	96	108
15	76	89	102	115

Example: An 8-year-old 30-kg (≈66-lb) dog—large—is roughly 60 human years.

Life stages by size

• Puppy/Adolescent (up to ~24 dog months): growth, socialization, basic cues, start dental care.
• Adult (2–6 years small/medium, 2–5 years large): maintain fitness and ideal weight; monitor teeth and bloodwork.
• Senior (from ~7 small/medium, ~6 large, ~5 giant): check joints, heart, teeth, and eyes more often; keep training short but frequent.

Staying healthy: checkups & prevention

• Manage weight: lean is healthier—ribs palpable, waist visible.
• Feed high-quality food & weigh portions; seniors may need lower-calorie, protein-rich diets (ask your veterinarian).
• Brush teeth 3–5×/week to reduce tartar and inflammation.
• Daily activity: a mix of walks, scent work, and short training sets.
• Vet check: once yearly blood/urine; twice yearly for seniors. Keep vaccines and parasite control up to date.
• Senior care: non-slip floors, orthopedic bed, limit stairs and jumping.

Frequently asked questions (FAQ)

Is there an exact formula?
No. Some scientific models (e.g., logarithmic curves for specific breeds) exist, but none fit all dogs. The chart above is a practical guide.

What accelerates aging?
Excess weight, dental disease, chronic stress, too little exercise/mental work, and untreated medical conditions.

How do I spot signs of aging?
Graying muzzle, longer recovery, stiffness, changed sleep, reduced vision/hearing, restlessness or forgetfulness (have your veterinarian assess).

PS: Use dog-to-human year conversions as guidance only—make health decisions with your veterinarian for your individual dog.