How this pet age calculator works
For dogs, it applies the combined function from a 2020 DNA-methylation study: human age = 16 × ln(dog age) + 31. For cats, it linearly interpolates International Cat Care's published age chart — a series of known points (6 months ≈ 10, 1 year ≈ 15, 2 years ≈ 24, then +4 per year) rather than a single formula, since cat aging doesn't follow a clean logarithmic curve the same way.
Sources
Dog formula and reference points: Wang, T., Ma, J., Hogan, A.N., et al., "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome", Cell Systems 11 (2020) — formula confirmed from the authors' own PDF (combined function, Figure 3D). Cat age chart: International Cat Care, "How to tell your cat's age in human years", developed with the AAHA and AAFP; life stage boundaries confirmed against the 2021 AAHA/AAFP Feline Life Stage Guidelines. Fetched September 18, 2026.
Questions
What formula converts dog years to human years?
The most current science-based formula comes from a 2020 study that mapped DNA-methylation changes in dogs onto the same changes in humans: human age = 16 × ln(dog age) + 31. It replaces the old "first year = 15, second = 9, then 5 per year after" rule, which the AVMA has since removed from its site.
Is the cat-years formula the same everywhere?
This calculator uses International Cat Care's published chart, developed jointly with the American Animal Hospital Association and the American Association of Feline Practitioners: the first year is 15 human years, the second brings the total to 24, and each year after that adds 4.
Why can't I enter a dog age under 0.15 years?
The DNA-methylation formula was fit to dogs from about 4 weeks old, but the equation itself only holds up from roughly 8 weeks onward — below that it produces negative, meaningless numbers. For very young puppies, milestone-based charts are more reliable than a single equation.
Does breed or size change the human-year conversion?
For dogs, yes in practice — small breeds tend to live longer and age more slowly than giant breeds, something one formula can't capture. The 2020 study's formula is a population average from Labrador retrievers, a medium-large breed, so treat it as a reasonable estimate rather than an exact figure for every breed.
More free tools
- Fuel cost calculator — Trip fuel cost and cost per mile from distance, economy, and pump price; MPG from two fill-ups.
- Houseplant watering calculator — How often to water 25 common houseplants, with your next watering dates.
- Sourdough hydration calculator — Dough hydration with levain included, or the water to hit a target, plus salt.
- Reef dosing calculator — Millilitres of alkalinity, calcium, or magnesium additive to reach a target, from your product label.
- Reading time calculator — Days to finish a book from your page pace, or pages per day to hit a deadline.
- Varroa mite calculator — Mites per 100 bees from an alcohol wash or sugar roll, with the 3% treatment flag.
- Film reciprocity failure calculator — Corrected long-exposure times for HP5 Plus, Tri-X, T-Max, Delta, Portra, Fomapan.
- Kiln firing cost calculator — Electric kiln firing cost from kilowatts, Orton cone, ramp rate, and electricity rate.
- Cut list optimizer — Guillotine cutting diagram and yield from stock and part sizes, kerf-aware.
- Board feet calculator — Total board feet and cost for a lumber order, across as many board sizes as you need.
- Miter angle calculator — Compound miter and bevel for crown molding, or a plain miter for baseboard and picture frames.
- Wood shelf sag calculator — Expected shelf sag from span, depth, thickness, material, and load, Sagulator-style.
- Dog & cat calorie calculator — Daily calories (RER/MER) from weight, species, and life stage or status, the standard veterinary formula.
- Whetstone angle calculator — Spine-lift height for a target sharpening angle, or the angle for a lift you used — freehand or guided rod.
- Wallpaper roll calculator — Rolls needed from wall width, ceiling height, roll size, pattern repeat, and door/window openings, metric or imperial.
- Dough temperature calculator — Water temperature to hit a target dough temp from room, flour, and levain temperature — the standard ×3/×4 baker's formula.
- Bee syrup calculator — Sugar to add for 1:1 spring or 2:1 fall syrup, by the correct weight-based ratio, with a cup measure.