Pet Medication Dosage Calculator

Pet medication dosage by weight is how animals get the right therapeutic amount, rather than too little to work or enough to poison them. Most veterinary drugs are dosed in milligrams per kilogram of body weight (mg/kg).

Core formula: Dose (mg) = Dog/Cat Weight (kg) × Dosage Rate (mg/kg) Tablets Needed = Dose (mg) ÷ Tablet Strength (mg) Liquid Volume (mL) = Dose (mg) ÷ Concentration (mg/mL)

Weight conversion: Weight (kg) = Weight (lbs) ÷ 2.2046

Common veterinary dosage rates. These are general reference figures, and every one of them is a range that your vet narrows for the individual animal. Always follow the prescription you were given rather than a table on a web page.

Worked example: A dog weighs 35 lbs. The vet prescribes amoxicillin at 10 mg/kg twice daily. Tablets available: 250 mg.

Weight (kg) = 35 ÷ 2.2046 = 15.9 kg Dose = 15.9 × 10 = 158.8 mg per dose Tablets per dose = 158.8 ÷ 250 = 0.64 tablets, which rounds to half a tablet (125 mg) on an ordinary single-scored tablet. Your vet may instead prescribe a single 250 mg tablet once daily, which delivers a similar total with fewer pills to split.

Half is not the arithmetically nearest fraction here, three quarters is, and that gap is exactly why the calculator prints the exact figure next to the practical one. Most tablets carry one score line down the middle and break into halves and nothing finer. A cross-scored tablet quarters cleanly and gets you closer. When the practical figure lands a long way from the exact one, that is a signal to ask for a different strength rather than to start shaving pills with a knife.

Watch the units in that table. Benadryl is the one people get wrong, because the familiar rule of thumb is 1 mg per pound, and a pound is not a kilogram. Written per kilogram it is 2.2 mg/kg. Enter 1 instead of 2.2 into the custom field and you have given less than half the intended dose.

Splitting tablets: the dropdown answers give a tablet count to two decimals, which is arithmetic rather than advice. In practice you can split a scored tablet in half, sometimes into quarters, and nothing finer. Unscored tablets, capsules and anything coated should not be split at all, because the coating is often what controls where the drug releases. When the number lands awkwardly, that is a question for the vet, who can usually prescribe a different tablet strength or a liquid.

Critical safety notes: Never dose cats with dog medications without explicit vet guidance. Acetaminophen (Tylenol) is fatally toxic to cats. Ibuprofen is toxic to both dogs and cats. Always confirm dosing with your veterinarian before administering any medication.