How the dose is calculated
Chocolate harms dogs through two related stimulants, theobromine and caffeine (together called methylxanthines). The calculator multiplies the amount eaten by the methylxanthine content of that type of chocolate, then divides by your dog's weight in kilograms. Vets use the same mg/kg measure.
Dose (mg/kg) = grams eaten × (theobromine + caffeine, mg per gram) ÷ dog's weight (kg)
1 oz = 28.35 g, 1 lb = 0.4536 kg
Worked example: a 20 lb dog
A 20 lb dog weighs 9.07 kg. If it eats a 1.55 oz (43.9 g) milk chocolate bar: 43.9 × 2.30 = 101 mg, and 101 ÷ 9.07 = 11.1 mg/kg. That is under the 20 mg/kg level where signs usually start. If the same dog eats one 1 oz square of unsweetened baking chocolate: 28.35 × 15.5 = 439 mg, or 48.4 mg/kg. That is in the range where heart effects are possible, from an amount a third of the size.
How much is in each type
| Type | Theobromine | Caffeine | Total used | Range in sources |
|---|---|---|---|---|
| White chocolate | 1.1 mg/oz | 0 | 1.1 mg/oz | 0–1.1 |
| Milk chocolate | 60 mg/oz | 6 mg/oz | 65 mg/oz | 64–65 |
| Semi-sweet or dark, up to 69% | 179 mg/oz | 24 mg/oz | 204 mg/oz | 150–204 |
| Bittersweet, 70–85% cacao | 227 mg/oz | 23 mg/oz | 250 mg/oz | 250 |
| Unsweetened baking | 417 mg/oz | 23 mg/oz | 440 mg/oz | 391–440 |
| Dry cocoa powder | 743 mg/oz | 65 mg/oz | 808 mg/oz | 649–808 |
| Cocoa bean mulch | not reported separately | 255 mg/oz | varies widely by product | |
Figures come from USDA FoodData Central lab values and the methylxanthine table in the Merck Veterinary Manual. Where they differ, we use the higher total so the estimate errs on the side of caution. Real bars vary by brand and cacao percentage, and Merck notes some mulch has had its methylxanthines removed, so treat any result near a threshold as the next level up.
Dose levels and what they mean
| Dose | What can happen |
|---|---|
| About 20 mg/kg | Mild signs: vomiting, diarrhea, extra thirst |
| 40–50 mg/kg | Heart effects: fast or irregular heartbeat |
| 60 mg/kg and up | Tremors and seizures |
| 100–200 mg/kg | Reported oral LD50 (the dose that kills half of dogs); severe signs and deaths can happen well below it |
These are the thresholds in the Merck Veterinary Manual chapter written by an ASPCA Animal Poison Control Center veterinarian. Puppies, older dogs and dogs with heart disease can react at lower doses.
Symptoms and timeline
Signs usually appear 6 to 12 hours after eating. Early signs are thirst, vomiting, diarrhea, a bloated belly and restlessness. They can progress to hyperactivity, frequent urination, wobbliness, stiffness, tremors and seizures. Severe cases can last up to 72 hours. The ASPCA also lists panting, abnormal heart rhythm and, rarely, death.
Why dogs are hit so hard
Dogs break down theobromine slowly. Its half-life in dogs is about 17.5 hours (caffeine's is 4.5 hours), so after a full day roughly 40% of the theobromine is still in the body. After the liver processes it, it is recycled back through the gut, and it can be reabsorbed from urine sitting in the bladder. That is why serious cases need fluids and nursing care for a day or more, not a single dose of medicine.
What not to do
- Do not make your dog vomit unless a vet or poison line tells you to. Vets do this only when the chocolate was eaten recently, ideally within about 2 hours, and the dog has no signs yet.
- Do not wait for symptoms before calling. Signs can take 6 to 12 hours, and treatment works best early.
- Do not guess low. Find the wrapper, note the cacao percentage, and count what is missing.
- Check the ingredients for xylitol, raisins or macadamia nuts, which are dangerous on their own.
When you call, have your dog's weight, the product name, roughly how much is gone and when it happened. Phone numbers were checked on the ASPCA and Pet Poison Helpline websites in October 2026.
Questions people ask
How much chocolate will hurt a dog?
It depends on the dog’s weight and the type of chocolate. The Merck Veterinary Manual puts mild signs at about 20 mg of theobromine and caffeine per kg of body weight, heart effects at 40–50 mg/kg and seizures at 60 mg/kg or more. For a 20 lb dog, that first level is about 2.8 oz of milk chocolate but only 0.4 oz of unsweetened baking chocolate.
Is white chocolate dangerous for dogs?
White chocolate has almost no theobromine, about 1 mg per ounce, so poisoning from it is very unlikely. The fat and sugar can still cause vomiting, diarrhea or pancreatitis, and some white chocolate treats contain other risky ingredients such as macadamia nuts, raisins or xylitol.
How long after eating chocolate will a dog get sick?
Signs usually start 6 to 12 hours after eating, according to the Merck Veterinary Manual, and severe cases can last up to 72 hours. A dog that looks fine an hour after eating chocolate is not in the clear yet.
Should I make my dog throw up after eating chocolate?
Only if a vet or poison control tells you to. Vets usually induce vomiting only when the chocolate was eaten recently, ideally within about 2 hours, and the dog has no signs yet. Doing it at home with the wrong product or dose can cause its own injuries.
Do the poison hotlines charge a fee?
Yes. Pet Poison Helpline lists an $89 per-incident fee that covers follow-up calls. The ASPCA Animal Poison Control Center says a consultation fee may apply. Both are open 24 hours a day, every day of the year. Your own vet or an emergency clinic is also a good first call.
Why does the calculator count caffeine as well as theobromine?
Chocolate contains both, and both are methylxanthines that act on a dog the same way. The Merck thresholds are given for methylxanthines, so the calculator adds the two. Theobromine is by far the bigger share in every type of chocolate.