Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Human-equivalent age
39.0
Life stage
Adult
Typical life expectancy (years)
13.0
Typical years remaining
8.0
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter species.
- 2Enter pet's age (years).
- 3Enter adult size (dogs).
- 4Read your human-equivalent age on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
The 'multiply by seven' rule is wrong at both ends of life. Dogs age fast in year one, then slow at a rate that depends on adult size, while cats follow a steadier curve. This calculator uses the size-banded AVMA-style mapping instead.
Worked example
Using the values the calculator loads with:
Inputs
- Species: Dog
- Pet's age: 5 years
- Adult size (dogs): Medium — 21–50 lb
Results
- Human-equivalent age: 39
- Life stage: Adult
- Typical life expectancy (years): 13
- Typical years remaining: 8
What each field means
Inputs
- Species
- Pick the option that matches your situation — the maths changes per option. Choices: Dog, Cat.
- Pet's age (years)
- The pet's age used in the calculation, measured in years. Starts at 5 years so you have a working example on load. Accepted range: 0–30 years.
- Adult size (dogs)
- Pick the option that matches your situation — the maths changes per option. Choices: Small — under 20 lb, Medium — 21–50 lb, Large — 51–100 lb, Giant — over 100 lb.
Results
- Human-equivalent age
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Life stage
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Typical life expectancy (years)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Typical years remaining
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why does size change dog aging so much?
Large breeds reach skeletal maturity later but age faster afterward. A Great Dane is functionally geriatric around six or seven, while a similar-aged terrier is barely middle-aged.
When does senior care start?
Most vets start twice-yearly exams and bloodwork at roughly 75% of expected lifespan — around seven for large dogs and ten for cats and small dogs.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Pet Age Calculator (Dog & Cat Years). Retrieved from https://www.revenuelab.fyi/toolbox/pet-age
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/pet-age" target="_blank" rel="noopener">Pet Age Calculator (Dog & Cat Years) — RevenueLab</a> (2026).</p>
Source: [Pet Age Calculator (Dog & Cat Years) — RevenueLab](https://www.revenuelab.fyi/toolbox/pet-age) (2026).