Pet Medication Dose Calculator
Double-check a vet-prescribed dose: turn a mg/kg, mg/lb or mcg/kg rate into milligrams, millilitres of liquid or tablets (rounded to halves or quarters), daily and course totals — or check what mg/kg a prescribed amount works out to. A dosing check, not a prescription.
How it works
Weight (kg) = weight (lb) × 0.4536 · Dose (mg) = weight (kg) × dose rate (mg/kg) — 1 mg/lb = 2.2 mg/kg, 1 mcg = 0.001 mg · Liquid volume (mL) = dose (mg) ÷ concentration (mg/mL) — 12.5 mg/5 mL = 2.5 mg/mL, 1% = 10 mg/mL · Tablets = dose ÷ tablet strength, rounded to the nearest piece you can give · Daily total = dose × doses a day · Check mode: rate (mg/kg) = amount given (mg) ÷ weight (kg) · Body surface area (m²) = K × weight (g)^⅔ ÷ 10,000, K = 10.1 for dogs and 10.0 for cats
Most animal medicines are dosed by body weight in milligrams per kilogram, so the dose is the pet’s weight in kilograms times that rate. Rates written per pound or in micrograms are converted for you. For a liquid or injectable, dividing the milligram dose by the concentration gives the volume to draw up, and the calculator names the smallest syringe that holds it; concentrations printed as “mg per 5 mL” or as a percentage are converted to mg/mL. For tablets it divides by the tablet strength and rounds to whole, half or quarter tablets, then shows the dose your pet actually gets and warns if rounding moves it more than 10%. With a dose range it picks the smallest tablet amount inside the range. Add how often and for how long to see daily and course totals. Check mode works backwards from what is on the prescription label to the mg/kg rate, so you can compare it with the leaflet. The body surface area estimate uses the standard veterinary formula for drugs dosed per square metre. None of this knows which drug, rate or schedule is right or safe for your animal — that depends on the species, age, kidney and liver function and other medicines, and only your vet can decide it.
Worked example
A 22 lb dog is 22 × 0.4536 ≈ 9.98 kg. At a 5 mg/kg dose that is 9.98 × 5 = 49.9 mg. If the liquid is 50 mg/mL, the volume is 49.9 ÷ 50 = 1.0 mL, which fits a 1 mL syringe. With 25 mg scored tablets instead, 49.9 ÷ 25 = 2.0, so 2 tablets (50 mg, 5.01 mg/kg). Given twice a day for 7 days, that is 14 doses and 28 tablets. Checking a label that says 0.8 mL of 50 mg/mL for the same dog: 0.8 × 50 = 40 mg ÷ 9.98 kg = 4.0 mg/kg, 20% below the 5 mg/kg rate — worth a quick question to the vet.
Sources: MSD Veterinary Manual — Weight to body surface area conversion for dogs · MSD Veterinary Manual — Weight to body surface area conversion for cats · U.S. FDA — Paws off xylitol; it’s dangerous for dogs · ASPCA — Protecting your pets from poisons · International Cat Care — Permethrin poisoning
Frequently asked questions
Can I use this to dose my pet at home?
No — use it only to double-check a dose your veterinarian has already prescribed or a rate printed on a veterinary product’s label for your species. Correct drugs, dose rates and frequencies differ by species, breed, age and health, and some human medicines are toxic to pets.
Why convert pounds to kilograms?
Veterinary doses are usually written in mg per kilogram, so weight must be in kilograms. One pound is about 0.4536 kg; a 22 lb pet is roughly 10 kg. If a leaflet gives the rate in mg/lb, choose mg/lb next to the dose and the calculator converts it (1 mg/lb = 2.2 mg/kg).
How do I turn a milligram dose into millilitres?
Divide the milligram dose by the liquid’s concentration in mg/mL. A 50 mg dose of a 50 mg/mL solution is 1 mL; the same dose of a 25 mg/mL solution is 2 mL. If the bottle says 12.5 mg per 5 mL, pick “mg per 5 mL” and the calculator does the conversion.
Can I split my pet’s tablets?
Only if the label or your vet says so — scored tablets are made to be halved, but coated, slow-release and many capsules must not be split. Choose whole, half or quarter pieces and the calculator shows how far rounding moves the dose. If the change is large, ask your vet about another strength or a liquid.
How do I check the dose on my pet’s prescription label?
Choose Check a prescribed dose, enter the amount per dose in mL, mg or tablets, and the rate from the leaflet. The calculator shows the mg/kg your pet is getting. A difference is a reason to ask your vet or pharmacist — vets sometimes prescribe outside the usual range on purpose, so never change a prescribed dose on your own.
Which human medicines are dangerous for pets?
Paracetamol (acetaminophen) is highly toxic to cats and dangerous to dogs; ibuprofen and naproxen can cause stomach ulcers and kidney failure in dogs and cats; and xylitol, a sweetener in some human syrups and chewables, is poisonous to dogs. If your pet has swallowed a human medicine, contact your vet or an animal poison line straight away.
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Educational estimate only — not veterinary advice. Always confirm any dose, diet or medication with your veterinarian before giving it to an animal.