Dog Years- Interesting!

It is often said that people live 7 times as long as dogs so each year of a dog's life is equal to 7 years of a human's life. This is inaccurate for two reasons:

• The longest-lived breeds have an average lifespan which is double that of the shortest-lived breeds. So one can only map years after considering the breed and other factors described above.
• Most breeds (especially the smaller breeds) have a relatively short childhood compare to people. A small dog with an expected lifespan of 15 years would be mature (sexually and physically) within 1 year. A man with an expected lifespan of 75 years (the current approximate male life expectancy in developed countries) would have the equivalent maturity at 15 years of age. Thus the dog reached maturity in 1/15th of its lifespan whereas the person was mature in 1/5th (15 years / 75 years) of his lifespan. Consequently, while one can say that the man is living 5 times as long as the dog, so each dog year is equal to 5 human years, the first year of life for the dog sees the same amount of development as in the first 15 or so human years. For this reason, an accurate mapping of dog years to human years needs to consider factors other than expected lifespan. The following table does this, considering the different development stages and the rates at which they are reached (on average) for the different sizes of dogs.

Size and Aging

Calendar Years	Under 20 lbs (9 kg)	20-50 lbs (9-23 kg)	50-90 lbs (23-41kg)	Over 90 lbs (over 41 kg)
1	15	15	14	12
2	23	24	22	20
3	28	29	29	28
4	32	34	34	35
5	36	38	40	42
6	40	42	45	49
7	44	47	50	56
8	48	51	55	64
9	52	56	61	71
10	56	60	66	78
11	60	65	72	86
12	64	69	77	93
13	68	74	82	101
14	72	78	88	108
15	76	83	93	115
16	80	87	99	123
17	84	92	104
18	88	96	109
19	92	101	115
20	96	105	120

The above table is based on averages. However, considering the additional factors (such as breed) discussed on this page would give a more accurate forecast for individual dogs. The oldest recorded age for a dog is 27 years.

So that means that a dog under 20 lbs at 5 months is about10 years old in people years, 8 months is 13 years, and so on, following the table above. Cool huh?