Dewormer Dose by Weight Calculator for Dogs and Cats
Work out a dewormer dose from your pet’s weight: milligrams and millilitres from any label mg/kg rate, or the label amount for fenbendazole granules, pyrantel suspension and praziquantel tablets for dogs and cats, with species and age safety checks.
How it works
Dose (mg) = weight (kg) × label rate (mg/kg) · weight (kg) = weight (lb) ÷ 2.2046 · liquid volume (mL) = dose (mg) ÷ concentration (mg/mL); 10% = 100 mg/mL · tablets = dose ÷ mg per tablet · label presets: fenbendazole 50 mg/kg daily × 3 days; pyrantel 4.54 mg/mL at 5 mL per 10 lb; praziquantel by the label weight bands
Dewormers are dosed by body weight, and getting it right matters both ways: too little leaves worms alive to keep shedding eggs and encourages resistance, while some active ingredients are toxic in overdose or in the wrong species. For most products the calculation is simple: weight in kilograms times the label rate in mg/kg gives the milligrams, and for a liquid, milligrams divided by the concentration on the bottle gives the millilitres to draw up. Rates in mcg/kg (micrograms, used for ivermectin-type drugs) are 1,000 times smaller than mg/kg, which is the most dangerous mix-up in pet dosing. Four common US label regimens are built in so you can check what the box says. Fenbendazole granules (Panacur C type) are 50 mg/kg once a day for three days, given as 1 g, 2 g and 4 g packets by weight band; pyrantel pamoate suspension at 4.54 mg/mL is 5 mL per 10 lb (about 5 mg/kg); praziquantel tablets are given by weight band, 34 mg tablets for dogs (up to 5 tablets) and 23 mg tablets for cats. The calculator blocks dog-only presets for cats and the reverse, and checks the label’s minimum age if you enter one. Other brands and strengths exist, so always read your own label. Safety comes first. Herding breeds such as Collies, Australian Shepherds and Shetland Sheepdogs can carry the MDR1 (ABCB1) mutation that makes ivermectin and related drugs reach the brain at normal doses; never use livestock or horse dewormers in dogs. Cats need cat-labelled products. Weigh the animal on the day, do not deworm a sick pet without a vet, and confirm the dose with your veterinarian and the product label.
Worked example
A 5 kg puppy and a product whose label rate is 10 mg/kg: 5 × 10 = 50 mg. From a 50 mg/mL liquid that is 50 ÷ 50 = 1.00 mL. With the fenbendazole granules preset, the same 5 kg (11.0 lb) puppy needs 5 × 50 = 250 mg a day for 3 days, which the label table rounds up to a 2 g packet a day. With the pyrantel preset it gets 11.0 lb ÷ 10 × 5 = 5.5 mL of suspension (25.0 mg).
Sources: Panacur C (fenbendazole) canine dewormer label: 50 mg/kg daily for 3 days, packet table · DailyMed: Nemex-2 (pyrantel pamoate 4.54 mg/mL) label · DailyMed: Droncit Canine Cestocide (praziquantel 34 mg) label · DailyMed: Droncit Feline Cestocide (praziquantel 23 mg) label · Merck Veterinary Manual: Safety of anthelmintics (MDR1/ABCB1 in herding breeds) · CAPC general guidelines (deworming puppies and kittens)
Frequently asked questions
Where do I find the mg/kg rate?
On the product label or package insert, and it differs by active ingredient: fenbendazole granules for dogs are 50 mg/kg daily for three days, pyrantel about 5 mg/kg once. Use the rate for your product and the parasite it targets, or the rate your vet gives you.
How much pyrantel do I give my dog?
For the common 4.54 mg/mL pyrantel pamoate suspension, the label dose is 1 teaspoon (5 mL) for each 10 lb of body weight, about 5 mg/kg. A 20 lb dog gets 10 mL. Shake the bottle well first.
Why calculate millilitres instead of just milligrams?
Liquid dewormers are measured with a syringe in millilitres, so the milligram dose has to be divided by the concentration on the bottle. Two products with the same active ingredient can have different strengths, so never reuse a volume from another product.
Can I use a dog dewormer for my cat?
Only if the product is labelled for cats, at the cat dose. Some dog products, notably permethrin spot-ons, are highly toxic to cats, and the dog-only presets here are blocked for cats. Ask your vet.
Is ivermectin safe for all dogs?
No. Dogs with the MDR1 (ABCB1) mutation, common in Collies, Australian Shepherds, Shetland Sheepdogs and related herding breeds, can be poisoned by ivermectin and similar drugs at normal doses. Never use horse or livestock ivermectin in dogs; use only vet-prescribed dog products.
How often should puppies be dewormed?
The Companion Animal Parasite Council recommends starting at 2 weeks of age and repeating every 2 weeks until a monthly broad-spectrum preventive is started. Your vet will set the exact schedule and product.
Related calculators
Educational estimate only, not veterinary advice. Always follow the product label and confirm the dose with a licensed veterinarian before deworming any animal.