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How Do Dog Years Work? The Real Math Behind Dog Years in 2026

How Do Dog Years Work? The Real Math Behind Dog Years in 2026 Dog years don't work on the old "1 year = 7" rule — the modern veterinary model is logarithmic, estimating a dog's human-age equivalent as roughly 16 × ln(dog's age) + 31, which puts a 1-year-old dog at about 31 human years and a 5-year-old at about 57, before breed size fine-tunes the curve; calculate your dog's age(/pets/dog-age-calculator) to get the exact number for your dog. That single formula, published by University of California San Diego researchers in the journal Cell Systems in July 2020, is why the "multiply by 7" shortcut quietly disappeared from veterinary offices. When we built UseCalcPro's dog age tool, we cross-checked three competing aging models against each other and re-derived the size curve by hand for all four weight classes. The number that reset our intuition was 31: the 2020 epigenetic-clock study...