What is the UC Davis epigenetic (DNA methylation) formula for dog age?

The UC Davis formula is Human Age = 16 * ln(Dog Age) + 31, published in Cell Systems (2020). While highly accurate at the cellular DNA level, it calculates a 1-year-old dog as 31 human years. We use the AAHA size-based model because it better reflects real-world physical development and accounts for weight differences across breeds.

Dog age chart

Dog years to human years by adult size

A quick reference for estimating your dog's human-equivalent age. Adult size changes the pace of aging, especially after the first two years.

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Small, medium, large, and giant dogs shown side by side

Dog years to human years chart by adult size
Dog age	Smallup to 20 lb	Medium21–50 lb	Large51–90 lb	Giantover 90 lb
1 year	15 human years	15 human years	15 human years	15 human years
2 years	24 human years	24 human years	24 human years	24 human years
3 years	28 human years	28 human years	30 human years	32 human years
4 years	32 human years	33 human years	35 human years	37 human years
5 years	36 human years	37 human years	40 human years	42 human years
6 years	40 human years	42 human years	45 human years	49 human years
7 years	44 human years	47 human years	50 human years	56 human years
8 years	48 human years	51 human years	55 human years	64 human years
9 years	52 human years	56 human years	61 human years	71 human years
10 years	56 human years	60 human years	66 human years	78 human years
11 years	60 human years	65 human years	72 human years	86 human years
12 years	64 human years	69 human years	77 human years	93 human years
13 years	68 human years	74 human years	82 human years	101 human years
14 years	72 human years	78 human years	88 human years	108 human years
15 years	76 human years	83 human years	93 human years	115 human years

Science Deep Dive

The Epigenetic DNA Formula vs. Size-Based Sizing

You might have seen the logarithmic formula from UC Davis researchers: Human Age = 16 × ln(Dog Age) + 31. It measures biological methylation changes, but pegs a 1-year-old puppy at 31 human years.

Our chart uses the AAHA clinical veterinary guidelines, adjusting for adult body mass because dogs of the same chronological age can have very different life-stage profiles.

These are estimates, not a medical measurement. Breed, health, lifestyle, and individual history also affect aging. Use the calculator for interpolation between table anchors and life-stage context.