18 Dog Years to Human Years

18 dog years is about 104 human years (AVMA medium dog) or 77 on the UCSD genetic formula.

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Formula

AVMA: 1st year ≈ 15, 2nd year +9 (24 total), each year after +5 (medium dog) · UCSD (Cell Systems, 2019): human age = 16 × ln(dog age) + 31, valid for dogs older than 1 year

Examples

InputResult
18 dog yearsAVMA 104 · UCSD 77
+1 yearAVMA 109 · UCSD 78

Frequently Asked Questions

How old is a 18-year-old dog in human years?

About 104 human years by the AVMA medium-dog guideline, or 77 by the UCSD genetic formula. An 18-year-old dog is about 104 human years (AVMA medium dog), exceptional longevity; small breeds reach this most often.

Why do the two methods give different numbers?

The AVMA curve is based on life-stage milestones (puppy, adult, senior); the UCSD formula is fitted to DNA methylation clocks. They agree on the early years and diverge for seniors, both are shown so you can judge.

Does breed size matter?

Yes. Small dogs live longer and age more slowly after year two (about +4 human years per dog year); giant breeds age faster (+6 or more). This calculator uses the medium-dog +5 curve.

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