Dog Age Calculator

Dog’s age: years

and months

Size

By size-

7x rule-

Scientific formula-

How dog years are calculated

There is no single exact answer, so this calculator shows three. By size: the first dog year counts as 15 human years, the second as 9 more (24 at age 2), then each extra year adds 4 (small), 5 (medium), 6 (large) or 7 (giant) human years, because bigger dogs age faster. 7x rule: the old rule of thumb, dog age times 7. Scientific formula: a 2020 study of DNA methylation in Labrador retrievers (Wang et al., Cell Systems) found human age is about 16 x ln(dog age) + 31; it is only shown from 6 months of age and was fitted on one breed, so treat it as a guide.

Dog age to human age chart

Dog age	Small	Medium	Large	Giant	7x rule	Scientific
1 year	15	15	15	15	7	31
2 years	24	24	24	24	14	42
3 years	28	29	30	31	21	49
4 years	32	34	36	38	28	53
5 years	36	39	42	45	35	57
6 years	40	44	48	52	42	60
7 years	44	49	54	59	49	62
8 years	48	54	60	66	56	64
9 years	52	59	66	73	63	66
10 years	56	64	72	80	70	68
11 years	60	69	78	87	77	69
12 years	64	74	84	94	84	71
13 years	68	79	90	101	91	72
14 years	72	84	96	108	98	73
15 years	76	89	102	115	105	74
16 years	80	94	108	122	112	75

FAQ

How old is a 1-year-old dog in human years?

About 15 human years by the size-based rule (roughly a teenager) and 7 by the old 7x rule. The scientific formula puts a 1-year-old Labrador near 31.

Is 1 dog year really 7 human years?

No, it is only a rough average. Dogs mature much faster than people in the first two years and then age more slowly, and large breeds age faster than small ones. That is why the size-based result differs from the 7x rule.

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

By the size-based rule about 56 (small), 64 (medium), 72 (large) or 80 (giant) human years. The 7x rule gives 70.

Do small dogs live longer than big dogs?

Generally yes: small breeds often reach 12 to 16 years while giant breeds commonly live 8 to 10, which is why the table adds more human years per dog year for bigger dogs.