When Is a Dog a Senior? Senior Dog Age by Size

Vets usually call a dog senior in the last quarter of its expected lifespan. For a large breed with an 11 year lifespan that is about 8, while small dogs living to 15 or more become seniors near 11. DogAgeCalc shows the life stage for your dog's size, starting here with a 10 year old large dog, which is about 66 in human years.

Senior dogs benefit from twice-yearly vet checks.

Dog age chart

Age	Small	Medium	Large	Giant	Cat
1	15	15	15	12	15
2	24	24	24	22	24
3	28	28	28	31	28
4	32	32	32	38	32
5	36	36	36	45	36
6	40	42	45	49	40
7	44	47	50	56	44
8	48	51	55	64	48
9	52	56	61	71	52
10	56	60	66	79	56
11	60	65	72	86	60
12	64	69	77	93	64
13	68	74	82	100	68
14	72	78	88	107	72
15	76	83	93	114	76
16	80	87	99	121	80

How the dog age calculator works

DogAgeCalc looks up your dog's age in the size-based chart above and interpolates between whole years, so 2 years and 6 months sits halfway between the year-two and year-three values. Past 16, it keeps adding the last yearly step for that size. Months under a year are spread evenly across the first year.

The DNA-based figure comes from a 2020 study of Labrador retrievers that compared chemical changes in DNA with those in people. It suggests human age ≈ 16 × ln(dog age) + 31, which makes young dogs much "older" than the chart: a 1 year old comes out at 31. It was measured in a single breed, so treat it as an interesting comparison rather than a rule.

Life stages

Dogs are puppies until about one year (18 months for giant breeds), young adults until three, and mature adults until the last quarter of their expected lifespan, when they become seniors. Typical lifespans used here are 15 years for small dogs, 13 for medium, 11 for large and 9 for giant breeds. Individual dogs vary a lot, so your vet's view always wins. Everything is calculated in your browser.

Frequently asked questions

At what age is a dog considered old?

From about 7 for giant breeds to about 11 for small dogs.

How long do dogs live?

Roughly 9 years for giant breeds to 15 or more for small dogs.

What changes for a senior dog?

Diet, exercise and checkups often change; ask your vet.

Is DogAgeCalc free?

Yes, with no sign-up or ads.

Is my pet's age saved?

Yes, in this browser only.

Senior dog age

Dog age chart

How the dog age calculator works

Life stages

Frequently asked questions

More tools

Age	Small	Medium	Large	Giant	Cat
1	15	15	15	12	15
2	24	24	24	22	24
3	28	28	28	31	28
4	32	32	32	38	32
5	36	36	36	45	36
6	40	42	45	49	40
7	44	47	50	56	44
8	48	51	55	64	48
9	52	56	61	71	52
10	56	60	66	79	56
11	60	65	72	86	60
12	64	69	77	93	64
13	68	74	82	100	68
14	72	78	88	107	72
15	76	83	93	114	76
16	80	87	99	121	80

Age	Small	Medium	Large	Giant	Cat
1	15	15	15	12	15
2	24	24	24	22	24
3	28	28	28	31	28
4	32	32	32	38	32
5	36	36	36	45	36
6	40	42	45	49	40
7	44	47	50	56	44
8	48	51	55	64	48
9	52	56	61	71	52
10	56	60	66	79	56
11	60	65	72	86	60
12	64	69	77	93	64
13	68	74	82	100	68
14	72	78	88	107	72
15	76	83	93	114	76
16	80	87	99	121	80

Age	Small	Medium	Large	Giant	Cat
1	15	15	15	12	15
2	24	24	24	22	24
3	28	28	28	31	28
4	32	32	32	38	32
5	36	36	36	45	36
6	40	42	45	49	40
7	44	47	50	56	44
8	48	51	55	64	48
9	52	56	61	71	52
10	56	60	66	79	56
11	60	65	72	86	60
12	64	69	77	93	64
13	68	74	82	100	68
14	72	78	88	107	72
15	76	83	93	114	76
16	80	87	99	121	80