Dog Age Calculator is a free browser tool that converts a dog's age to human years instead of using the old seven-year rule. Enter age (years and months, or a birthday) and expected adult size (Small, Medium, Large or Giant). It can also convert human years to dog years, and offers copy, share, print and CSV chart download.
The chart is based on the AKC age chart and covers ages 1 to 16. It runs in the browser, needs JavaScript and has no sign-up, with no paid tier or ads mentioned. The page says results are educational estimates, not veterinary advice, and cites AKC and UC Davis while stating neither endorsed it.
Dog ages do not map cleanly to a flat seven-year rule. This free calculator lets owners convert a dog's age to human years by age and size in one step.