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How much chocolate is toxic to a dog?

How much chocolate is toxic to a dog: signs start at about 20 mg of theobromine per kg. For a 20 kg dog, 200 g of milk chocolate or 25 g of baking chocolate.

If your dog has eaten chocolate in the last hour or two and you want a number, put the weight, the chocolate type and the amount into the chocolate toxicity calculator. It gives the dose in milligrams per kilogram and tells you which of the published severity bands that dose lands in. If the result says to call, call: your vet, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661. All three are open around the clock.

What follows is the reasoning behind that number, so you can sanity-check it yourself and understand why the answer for a Labrador and a Chihuahua is so different.

The poison is theobromine, and the unit is mg per kg

Chocolate poisons dogs through methylxanthines, mainly theobromine with a smaller contribution from caffeine. Dogs clear theobromine slowly — Merck gives the half-life as around 17.5 hours — which is why an amount that does nothing to an adult human can put a dog in hospital.

The dose that matters is not “how much chocolate” but “how much theobromine per kilogram of dog”. Two steps:

theobromine (mg) = grams eaten × theobromine per gram of that chocolate
dose (mg/kg)     = theobromine (mg) ÷ dog's weight (kg)

The published thresholds, per Merck, are:

Dose What to expect
under 20 mg/kg Below the level at which poisoning signs are normally seen. A rich, fatty snack can still cause vomiting or, rarely, pancreatitis.
20 mg/kg Mild signs: vomiting, diarrhea, thirst, restlessness, bloating.
40 mg/kg Cardiac signs: raised heart rate, arrhythmia, tremors, high blood pressure.
60 mg/kg Seizure risk.
100 mg/kg and up Potentially fatal.

Signs typically take 6 to 12 hours to appear. A dog that looks fine an hour after eating a large amount is not in the clear, and treatment is much more effective before signs start than after.

Why the type of chocolate changes everything

Theobromine comes from cocoa solids. The more cocoa, the more theobromine per gram, and the range across an ordinary kitchen spans more than three orders of magnitude:

Chocolate Theobromine, mg per gram
White chocolate 0.009
Milk chocolate 2.0
Semisweet or dark chips (45–59%) 5.3
Dark, 60–69% cocoa 6.5
Dark, 70–85% cocoa 8.0
Unsweetened baking chocolate 15.6
Unsweetened cocoa powder 25.6

Milk chocolate is what most candy bars, filled bars and advent calendars are made of. Dark chocolate is three to four times as concentrated. Baking chocolate and cocoa powder are the dangerous ones: a few squares of baking chocolate is a serious dose for a small dog.

White chocolate contains almost no theobromine and is not a poisoning risk in the usual sense. The fat and sugar can still upset a stomach or, in a susceptible dog, trigger pancreatitis.

Worked examples

Take the 20 mg/kg threshold, where mild signs begin, and turn it into grams of chocolate:

  • Milk chocolate: 20 ÷ 2.0 = 10 g of chocolate per kg of dog. A 20 kg (44 lb) dog reaches the mild band at about 200 g — four or five standard candy bars. A 5 kg (11 lb) dog gets there at 50 g, one bar.
  • Dark chocolate (70%): 20 ÷ 8.0 = 2.5 g per kg. A 20 kg (44 lb) dog reaches the threshold at 50 g, half a bar. A 5 kg (11 lb) dog at 12.5 g, a couple of squares.
  • Baking chocolate: 20 ÷ 15.6 ≈ 1.3 g per kg. A 20 kg (44 lb) dog at about 26 g, one square of a baking bar. A 5 kg (11 lb) dog at about 6 g.

The same arithmetic with 40 and 60 mg/kg gives the cardiac and seizure thresholds: simply double and triple the gram figures.

One conversion trap: American veterinary references usually quote theobromine in milligrams per ounce, not per gram. An ounce is about 28 grams. Mixing the two up is the single most common way a home calculation goes wrong by a factor of nearly thirty. The calculator works in grams throughout.

What to do if your dog has eaten chocolate

  1. Find the wrapper. Net weight and cocoa percentage let a vet compute the dose precisely instead of guessing.
  2. Work out the dose, or let the calculator do it.
  3. Call if the dose is at or above 20 mg/kg, or if you are unsure of the amount. Under 20 mg/kg, watch the dog for 12 hours and call if you see vomiting, diarrhea, restlessness or a racing heart.
  4. Do not induce vomiting at home unless a vet or poison line tells you to. It can be dangerous in a dog that is already tremoring, and unnecessary in a dog that is not at a toxic dose.

If your dog is seen within a couple of hours of eating, the vet will usually induce vomiting and give activated charcoal, often repeated because theobromine is reabsorbed from the gut. At higher doses treatment is supportive — fluids, heart rate control, seizure control, monitoring — and dogs are often kept in for 24 to 72 hours while the theobromine clears.

Beyond the candy bar

Cocoa bean mulch, sold for gardens, contains about 9 mg of theobromine per gram and smells of chocolate, which is exactly why dogs eat it. Cocoa powder, at 25.6 mg per gram, is the most concentrated form in a normal kitchen: a dog that gets into the baking cupboard has done something very different from a dog that stole a milk chocolate bar. Both are options in the calculator.

The weight you enter matters as much as the chocolate. If you only know a vague figure, weigh your dog on the bathroom scale — hold the dog, weigh, then weigh yourself and subtract. If the dog is overweight, the ideal weight calculator is not what you want here: toxicity is dosed on actual body weight, not target weight.

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