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Aging by Breed Size

Larger dogs age faster than smaller ones. Here's how the math breaks down across all four size categories.

The Veterinary Formula

Year 1
= 15 human years
All sizes
Year 2
+9 years (24 total)
All sizes
Year 3+
+4–7 per year
Varies by size

Small

Under 20 lbs

+4 yrs / dog year (after yr 2)

Chihuahua, Pomeranian, Shih Tzu, Dachshund

1yr
15
human yrs
2yr
24
human yrs
3yr
28
human yrs
5yr
36
human yrs
7yr
44
human yrs
10yr
56
human yrs
12yr
64
human yrs
15yr
76
human yrs
18yr
88
human yrs
20yr
96
human yrs

Medium

20–50 lbs

+4 yrs / dog year (after yr 2)

Beagle, Border Collie, Cocker Spaniel, Bulldog

1yr
15
human yrs
2yr
24
human yrs
3yr
28
human yrs
5yr
36
human yrs
7yr
44
human yrs
10yr
56
human yrs
12yr
64
human yrs
15yr
76
human yrs
18yr
88
human yrs
20yr
96
human yrs

Large

50–90 lbs

+5 yrs / dog year (after yr 2)

Labrador, Golden Retriever, German Shepherd, Boxer

1yr
15
human yrs
2yr
24
human yrs
3yr
29
human yrs
5yr
39
human yrs
7yr
49
human yrs
10yr
64
human yrs
12yr
74
human yrs
15yr
89
human yrs
18yr
104
human yrs
20yr
114
human yrs

Giant

90+ lbs

+7 yrs / dog year (after yr 2)

Great Dane, Saint Bernard, Mastiff, Irish Wolfhound

1yr
15
human yrs
2yr
24
human yrs
3yr
31
human yrs
5yr
45
human yrs
7yr
59
human yrs
10yr
80
human yrs
12yr
94
human yrs
15yr
115
human yrs
18yr
136
human yrs
20yr
150
human yrs

Side-by-Side Comparison

Dog AgeSmallMediumLargeGiant
1 year15151515
2 years24242424
3 years28282931
5 years36363945
7 years44444959
10 years56566480
12 years64647494
15 years767689115
18 years8888104136
20 years9696114150

Based on standard veterinary aging formula