Dog years calculator

Enter your dog's age and size to see their age in human years, by the veterinary size chart and by the 2020 DNA methylation formula, side by side.

By the Calcist team · Checked against known answers · Updated October 29, 2026

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Next: Got a cat too? Try the cat years calculator. Raising a puppy? See the puppy weight calculator.

Two ways to convert dog years to human years

1. The size chart. Veterinary groups use a chart that counts the first year of a dog's life as about 15 human years and the second as about 9 more, then adds 4 to 9 years for each dog year depending on size, because big dogs age faster and live shorter lives. The chart below is the one AAHA publishes (adapted from the Dog Owner's Home Veterinary Handbook), and the AVMA's charts give the same figures for small and very large dogs.

2. The DNA formula. In 2020, researchers at UC San Diego (Wang et al., Cell Systems) compared age-related chemical changes in dogs' and people's DNA, called methylation, and found a single formula:

Human age = 16 × ln(dog's age in years) + 31

ln is the natural logarithm. The formula says dogs age very fast early on: a 1-year-old matches a 31-year-old in DNA terms, then aging slows. It was built from 104 Labrador retrievers, so it fits medium-to-large dogs best.

Worked example

A 10-year-old medium dog (21–50 lb): the chart says 60 human years. The DNA formula gives 16 × ln(10) + 31 = 16 × 2.303 + 31 = 67.8. The old "times 7" rule would say 70.

Dog age chart in human years

Dog age	Small	Medium	Large	Giant	DNA formula
1	15	15	15	15	31
2	24	24	24	24	42
3	28	28	30	32	49
4	32	33	35	37	53
5	36	37	40	42	57
6	40	42	45	49	60
7	44	47	50	56	62
8	48	51	55	64	64
9	52	56	61	71	66
10	56	60	66	78	68
11	60	65	72	86	69
12	64	69	77	93	71
13	68	74	82	101	72
14	72	78	88	108	73
15	76	83	93	115	74
16	80	87	99	123	75
17	84	92	104	—	76
18	88	96	109	—	77
19	92	101	115	—	78
20	96	105	120	—	79

Giant-breed column ends at 16 because the chart doesn't list older giant dogs.

When is a dog a senior?

The AVMA says dogs become seniors in the last 25% of their breed's expected lifespan: about 8–11 years for small dogs, 8–10 for medium, 8–9 for large and 6–7 for giant breeds. Seniors benefit from more frequent checkups, so ask your vet how often to come in.

Limits

Both methods are approximations. Breed, genes, weight and health all affect how fast a dog ages.
The DNA formula was based on one breed and isn't meant for very young puppies.
For fractional ages, the calculator draws a straight line between the chart's whole years.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

10-year-old medium dog: 60 human years on the size chart ✓
10-year-old dog by the DNA formula: 16 × ln(10) + 31 = 67.8 ✓
2 years 6 months, large dog: 27 human years (between chart rows) ✓
7-year-old giant dog: 56 on the chart, and a senior ✓
17-year-old giant dog (edge: past the chart) uses the DNA formula: 76.3 ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

How do you convert dog years to human years?

The first dog year is about 15 human years, the second about 9 more, and each year after adds about 4 (small dogs) to 9 (giant dogs). A DNA-based formula, 16 × ln(age) + 31, gives a different curve.

Is one dog year really seven human years?

No. The 7-to-1 rule is a myth. Dogs grow up much faster than that in their first two years, then age more slowly, and big dogs age faster than small ones.

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

56 for a small dog, 60 for a medium dog, 66 for a large dog and 78 for a giant dog, by the chart. The DNA formula says about 68.

What is the dog years formula from UC San Diego?

Human age = 16 × ln(dog age) + 31, from Wang et al., Cell Systems (2020), based on DNA methylation in Labrador retrievers.

Related calculators

Cat years calculatorCat age in human years and life stage, from the vet chart.Puppy weight calculatorEstimate your puppy's adult weight from age, weight and breed.Age calculatorExact age in years, months and days, plus the next birthday.

Dog age	Small	Medium	Large	Giant	DNA formula
1	15	15	15	15	31
2	24	24	24	24	42
3	28	28	30	32	49
4	32	33	35	37	53
5	36	37	40	42	57
6	40	42	45	49	60
7	44	47	50	56	62
8	48	51	55	64	64
9	52	56	61	71	66
10	56	60	66	78	68
11	60	65	72	86	69
12	64	69	77	93	71
13	68	74	82	101	72
14	72	78	88	108	73
15	76	83	93	115	74
16	80	87	99	123	75
17	84	92	104	—	76
18	88	96	109	—	77
19	92	101	115	—	78
20	96	105	120	—	79

Dog age	Small	Medium	Large	Giant	DNA formula
1	15	15	15	15	31
2	24	24	24	24	42
3	28	28	30	32	49
4	32	33	35	37	53
5	36	37	40	42	57
6	40	42	45	49	60
7	44	47	50	56	62
8	48	51	55	64	64
9	52	56	61	71	66
10	56	60	66	78	68
11	60	65	72	86	69
12	64	69	77	93	71
13	68	74	82	101	72
14	72	78	88	108	73
15	76	83	93	115	74
16	80	87	99	123	75
17	84	92	104	—	76
18	88	96	109	—	77
19	92	101	115	—	78
20	96	105	120	—	79

Dog age	Small	Medium	Large	Giant	DNA formula
1	15	15	15	15	31
2	24	24	24	24	42
3	28	28	30	32	49
4	32	33	35	37	53
5	36	37	40	42	57
6	40	42	45	49	60
7	44	47	50	56	62
8	48	51	55	64	64
9	52	56	61	71	66
10	56	60	66	78	68
11	60	65	72	86	69
12	64	69	77	93	71
13	68	74	82	101	72
14	72	78	88	108	73
15	76	83	93	115	74
16	80	87	99	123	75
17	84	92	104	—	76
18	88	96	109	—	77
19	92	101	115	—	78
20	96	105	120	—	79