Dog Age Calculator
Estimate a dog’s human-age equivalent using a general rule of thumb.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
A rough age comparison based on a general veterinary rule of thumb: about 15 human years for a dog’s first year, 9 for the second, then about 5 per year. It is an analogy, not a measure of health, development, or life expectancy; dogs vary individually. Choose years and months or a birth date and reference date. Both use the same simplified curve, without breed or size adjustments.
Worked example
calculated with the default values below
Age input Years and months · Dog age 5 years · Extra months 0 months · Birth date (optional) 2020-10-31 · Today 2026-10-31 Human years equivalent 39.0 years · Dog age 5.00 years
Method and assumptions
H = 15 × min(A,1) + 9 × min(max(A−1,0),1) + 5 × max(A−2,0) A includes months ÷ 12. General rule of thumb only: 15 human years for dog year one, 9 for year two, then about 5 per year; not a health or lifespan assessment. A rough age comparison based on a general veterinary rule of thumb: about 15 human years for a dog’s first year, 9 for the second, then about 5 per year. It is an analogy, not a measure of health, development, or life expectancy; dogs vary individually. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Data sources
The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
H = 15 × min(A,1) + 9 × min(max(A−1,0),1) + 5 × max(A−2,0)
- A
- dog age, years
- H
- human-equivalent age
A includes months ÷ 12. General rule of thumb only: 15 human years for dog year one, 9 for year two, then about 5 per year; not a health or lifespan assessment.
Frequently asked questions
What should I know about this estimate?
A rough age comparison based on a general veterinary rule of thumb: about 15 human years for a dog’s first year, 9 for the second, then about 5 per year. It is an analogy, not a measure of health, development, or life expectancy; dogs vary individually.
Which inputs and limits apply to Dog Age Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Dog age: 0–30 years; Extra months: 0–11 months H = 15 × min(A,1) + 9 × min(max(A−1,0),1) + 5 × max(A−2,0) A includes months ÷ 12. General rule of thumb only: 15 human years for dog year one, 9 for year two, then about 5 per year; not a health or lifespan assessment. A rough age comparison based on a general veterinary rule of thumb: about 15 human years for a dog’s first year, 9 for the second, then about 5 per year. It is an analogy, not a measure of health, development, or life expectancy; dogs vary individually. The references provide context and limitations. They do not validate this page’s illustrative multipliers, lookup values or predictions.
What is a complete worked example for Dog age = 5 years; Extra months = 0 months?
Inputs: Dog age = 5 years; Extra months = 0 months. Calculation: H = 15 × min(A,1) + 9 × min(max(A−1,0),1) + 5 × max(A−2,0). Results: Human years equivalent = 39.0 years; Dog age = 5.00 years.