Dog years chart

Every age from 1 to 20, converted four ways by adult size — plus the epigenetic formula for comparison. This is the table behind the DogYears calculator.

Dog age	Small (<20 lb)	Medium (21–50 lb)	Large (51–90 lb)	Giant (>90 lb)	DNA formula
1 yr	15	15	15	15	31
2 yr	24	24	24	24	42.1
3 yr	28	29	30	31	48.6
4 yr	32	34	36	38	53.2
5 yr	36	39	42	45	56.8
6 yr	40	44	48	52	59.7
7 yr	44	49	54	59	62.1
8 yr	48	54	60	66	64.3
9 yr	52	59	66	73	66.2
10 yr	56	64	72	80	67.8
11 yr	60	69	78	87	69.4
12 yr	64	74	84	94	70.8
13 yr	68	79	90	101	72
14 yr	72	84	96	108	73.2
15 yr	76	89	102	115	74.3
16 yr	80	94	108	122	75.4
17 yr	84	99	114	129	76.3
18 yr	88	104	120	136	77.2
19 yr	92	109	126	143	78.1
20 yr	96	114	132	150	78.9

How the chart is built

Years one and two are shared by every size. The first year of a dog's life corresponds to roughly 15 human years — puppies develop that fast — and the second year adds about 9, bringing the total to 24. Up to this point a Chihuahua and a Great Dane are on the same track.

From year three, size takes over. Each further year adds about 4 human years for a small dog, 5 for a medium dog, 6 for a large dog and 7 for a giant breed. That is why the columns diverge so sharply at older ages: at 15, the spread between small and giant is 40 human years (76 versus 116).

The DNA formula column is different in kind. It comes from methylation-clock research (16 × ln(age) + 31) and was fitted on Labrador Retrievers, so it has no way to express size. It runs higher than the chart in the middle years and lower at the extremes. We print it alongside rather than blending the two, because they are answers to slightly different questions — see the formula explained.

These are population-level estimates for comparison. Individual dogs vary with breed, weight, health and luck, and none of this replaces a vet's judgement about your dog.

Questions about the chart

How do I read the dog years chart?

Find your dog's age in the first column, then read across to the column matching their adult size. A 7-year-old large dog, for example, reads 56 human years. The final column is the DNA epigenetic formula, which is the same for every size because the underlying study used one breed.

Why does the chart have four different answers for the same age?

Because dogs genuinely age at different rates by size. Small dogs mature quickly but then age slowly and live longer; giant breeds do the opposite. A single column would have to lie about at least three of the four groups.

Does the chart work for mixed-breed dogs?

Yes — use the size band your dog fits as an adult, based on weight. Mixed breeds follow the same size-driven pattern; if your dog sits on a boundary between bands, read both columns and treat the range as the honest answer.

Use the calculator instead