Pet calculators that show their working
Most pet calculators are one line of arithmetic behind a nice button. We went to the raw veterinary data — 8.5 million weight records — recomputed the growth curves ourselves, then tested the predictions against what those dogs actually grew into. Then we published the error bars.
- Weight records used
- 8.5M
- Dogs in the source data
- 3.5M
- Held-out accuracy test
- 64K dogs
- Our stated range holds
- 79.9%
Calculators
Puppy Weight Calculator
How big will your puppy get? Built from 8.5 million real vet weight records, with a measured error range instead of a confident guess.
Puppy Growth Chart
What puppies of each adult size actually weigh, week by week — including the early weeks the published charts leave out.
Dog Age Calculator
Life stage and human years, using your breed's own measured lifespan from 155 breeds — plus an honest account of where the usual formula comes from. Nowhere, it turns out.
Dog Age Chart
The chart, built from your breed's own measured lifespan — with the version everyone copies shown greyed out, because we couldn't find its source.
Cat Age Calculator
Life stage and how many more years your cat can expect, from a real UK life table — not the +4-a-year chart the guidelines deleted.
Dog Food Calculator
How much to feed your dog — and where that formula really comes from. It isn't the NRC, whatever every other calculator tells you.
Cat Calorie Calculator
Using the formula the current AAHA/AAFP feline guidelines actually publish, which isn't the one everyone else uses.
Every tool here had to clear the same bar: source it properly, or don't ship it. The feeding calculators took the longest — the "standard" formula turns out to trace to a textbook, not a guideline, and we weren't going to repeat that without saying so on the page. We'd rather ship a few that are genuinely the best on the web than ten that run the same unsourced formula as everyone else.
Guides
How long do dogs live?
The full 155-breed table — and why breed beats size twelvefold.
How big will my puppy get?
What actually predicts adult size — and the popular formula that doesn't.
How to calculate your dog's age
Why × 7 is wrong, and what to use instead.
When is a dog senior?
Why a Great Dane is old at 6 and a Chihuahua isn't.
Why trust a number from a website?
You shouldn't, on faith. So we made it checkable instead.
The data is public
Salt et al. (2017), PLoS ONE, released CC BY 4.0. Anyone can download it and check us.
The method is written out
Including where we depart from the published paper, and why — plus the checks that didn't go our way.
The accuracy is measured
On 63,993 dogs held out of the fitting. Not a claim — a test.
We also don't carry a "vet reviewed" badge, because we haven't earned one. Here's why that matters.