Cat Chocolate Toxicity Calculator
Cats rarely eat chocolate by choice, which makes any exposure worth taking seriously by weight.
The formula
theobromine mg/kg = grams eaten * mg per gram / body weight
The dose is theobromine, not chocolate
What matters is not how much chocolate was eaten but how much theobromine it contained, and that varies roughly eightfold between milk chocolate and baking chocolate. A biscuit's worth of milk chocolate is usually nothing; the same weight of cocoa powder is a serious problem for a small dog.
Why dogs and not us
Theobromine is a methylxanthine, chemically close to caffeine. Humans clear it in a few hours; dogs take around 17, so it accumulates to concentrations we never reach. The toxicity is not a property of the chemical so much as of how slowly the dog's liver disposes of it.
Do not wait for signs
Signs typically begin two to four hours after eating, but the treatments that work best — decontamination in particular — work best before that. If the quantity is anywhere near the thresholds below, the correct action is to telephone a vet now rather than to watch and see.
This does not replace a veterinarian
Every figure on this page comes from a published reference range, and a range is what it stays. The right dose for an individual animal depends on its kidney and liver function, on what else it is taking, on whether it is pregnant or very young or very old, and on what is actually wrong with it — none of which arithmetic can see. Use this to understand the scale of a dose or an exposure, and to have a better conversation with your vet. Do not use it to start, stop or change a medication.
If you believe your animal has swallowed something toxic, do not wait to see whether signs develop. Contact your veterinarian or an animal poison line immediately — in most poisonings the treatment that works is the one given early.