All 35 calculators

How to pick the right tool

The calculators fall into three groups, and knowing which one you are in matters more than picking the exact tool. Emergency triage — the toxicity calculators — answers a single question: is this dose serious enough to call someone right now? Those pages give you a severity band and the regional hotline numbers, and they are deliberately blunt, because the cost of underreacting to a xylitol exposure is far higher than the cost of an unnecessary phone call. Routine numbers — calories, portion sizes, water intake, ideal weight — are the ones worth revisiting every few months as your pet ages or gains weight. And planning tools — lifetime cost, crate size, litter box count — you use once, early, and rarely need again.

Where the numbers come from

Every calculator here derives from published veterinary sources rather than a rule of thumb someone repeated online. Calorie tools use the standard RER × MER method with NRC life-stage multipliers. Dog aging uses the AKC size-based curve, with the Wang epigenetic-clock formula offered alongside it so you can see how much the two disagree — because they do, sometimes by years. Feline life stages follow the AAFP/AAHA guidelines. Toxicity thresholds come from ASPCA Animal Poison Control and Pet Poison Helpline published dose data, cross-checked against the Merck Veterinary Manual.

Each page shows its own sources and states its assumptions. Where a figure is a regional estimate rather than a measurement — retail prices, for instance — it says so, because a confident-looking number with no provenance is worse than no number.

What these tools cannot do

A calculator works from the numbers you give it, and the most common source of a wrong answer is a wrong input — a guessed weight, or a dose of chocolate nobody actually measured. When you are estimating, estimate toward the cautious end. More importantly, none of these outputs are a diagnosis. A calorie figure will not tell you why a cat is losing weight, and a stool-color guide will not tell you why the color changed. They are built to help you have a better-informed conversation with your vet, and to help you recognize when that conversation needs to happen today rather than at the next check-up.

If your pet has an existing condition — kidney disease, diabetes, pancreatitis, a heart murmur — treat every figure here as a starting point your vet should adjust. Therapeutic diets and restricted-protein plans in particular override the general-population math these tools use.