Dog age chart: human years by dog size

The same birthday can look different for a Chihuahua and a Great Dane. Compare all four size estimates, or choose your dog’s size and calculate their age in months.

Dog years to human years by size

Dog years to human years by size
Dog age	Small	Medium	Large	Giant
1 year	15	15	15	15
2 years	24	24	24	24
3 years	28	28	29	31
4 years	32	32	34	38
5 years	36	37	39	45
6 years	40	42	44	49
7 years	44	47	49	56
8 years	48	51	54	64
9 years	52	56	59	71
10 years	56	60	64	79
11 years	60	65	69	86
12 years	64	69	74	93
13 years	68	74	79	100
14 years	72	78	83	107
15 years	76	83	88	114
16 years	80	87	93	121

Columns show estimated human years. Calculator size bands: Small under 22 lb; Medium 22–55 lb; Large 55–99 lb; Giant over 99 lb. These broad bands are starting points, not clinical boundaries.

How to read this dog age chart

Find your dog’s actual age in the first column, then follow the row to their size category. A 10-year-old small dog has an estimate of 56 human years, while a giant dog of the same age has an estimate of 79. For a partial year, use the calculator’s years and months fields.

Choose adult size for a growing dog

For a puppy, use expected adult size rather than current puppy weight. For a mixed breed, an estimated adult size is a practical starting point. If your dog is near a boundary, compare neighboring columns rather than treating one number as exact.

Why one dog year is not always seven human years

Our tables assign about 15 human years at age 1 and 24 at age 2, then diverge by size. A fixed seven-times rule misses both that early growth and the differences in later years. The calculator interpolates between table entries; it does not measure biological age.

What a breed page adds

Our 30 breed guides choose a starting size for familiar breeds. They use these same size tables, rather than a separately validated aging equation for every breed. Adjust the selected size to suit your dog, especially for breeds that come in several sizes.

What the number cannot tell you

AAHA notes that a dog’s life stage depends on more than chronological age, with breeds aging at different rates. Human-year estimates do not diagnose a condition, determine a care schedule, or forecast remaining lifespan. Use your dog’s own history and your veterinarian’s advice for those decisions.

Common questions

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

Our tables estimate 44 for small dogs, 47 for medium dogs, 49 for large dogs, and 56 for giant dogs.

How old is a 12-year-old dog in human years?

The estimates are 64 for small dogs, 69 for medium dogs, 74 for large dogs, and 93 for giant dogs. They are comparisons, not lifespan predictions.

Which size should I use for a mixed-breed dog?

Use an estimated adult size. If that estimate is uncertain or near a boundary, compare two size categories and treat the result as a range.

Does the calculator work beyond age 16?

Yes, but it extends the final slope of the relevant table. Results beyond the published table points are extrapolations and should be treated with extra caution.

Sources and calculation notes

Written by PetAgeNow. Numbers come from our own calculator tables. Veterinary resources provide life-stage context and do not endorse or validate this calculator.

Age comparisons are educational estimates. They do not predict health, behavior, or lifespan.