Pet Medication Dosage Calculator
Calculate safe OTC medication doses for dogs & cats
This calculator provides general dosage guidelines for common over-the-counter medications sometimes used for pets under veterinary guidance. Dosages are based on widely published veterinary references. Individual pets may have conditions or take other medications that make these doses unsafe. Never medicate your pet without veterinary approval.
Free pet medication dosage calculator for dogs and cats. Calculate safe doses for Benadryl, Pepto-Bismol, Melatonin, Fish Oil, Glucosamine and more.
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What this page assumes, and where it stops
Jurisdiction
General veterinary information for the United States.
Assumptions
- Only what you enter on this page is used. Personal circumstances, exemptions, and special cases are not applied.
- Results are estimates for orientation, not determinations.
- Everything runs in your browser. Nothing you type is sent to a server.
Where you should not rely on this
Never dose an animal from an online calculator. Species, breed, weight, age, and existing conditions all change what is safe, and several common human medicines are toxic to pets. Contact a veterinarian, or a poison control line in an emergency.
Official sources
Page reviewed 2026-09-04 · rules current as of that review were not independently verified against every jurisdiction · next review scheduled annually
Frequently asked questions
How is the dose worked out?
By body weight. Each medicine in the list carries a dose per kilogram and a maximum per kilogram, and the page multiplies that by the weight you enter.
Can I use a dog dose for a cat?
No. The page keeps separate lists for dogs and cats because several medicines that are routine for dogs are dangerous for cats. Pick the right species first.
Is this enough to medicate my pet?
No. Treat it as a sanity check on a dose your veterinarian has already given you. Condition, age, kidney and liver function and other medicines all change the safe amount. Ask your vet before giving anything.
How weight-based dosing is calculated
Veterinary doses are written per unit of body weight, almost always as milligrams per kilogram (mg/kg). The arithmetic is one multiplication: dose in milligrams = mg/kg figure × the animal’s weight in kilograms. Two things go wrong in practice, and neither is the multiplication.
The first is units. A weight taken in pounds has to be converted before it touches a mg/kg figure: divide pounds by 2.2046 to get kilograms. Using pounds directly in a mg/kg formula overdoses the animal by a factor of about 2.2.
| Weight | In kilograms |
|---|---|
| 5 lb | 2.27 kg |
| 10 lb | 4.54 kg |
| 20 lb | 9.07 kg |
| 45 lb | 20.41 kg |
| 70 lb | 31.75 kg |
The second is concentration. A dose in milligrams still has to be turned into a volume or a number of tablets, and that depends on the strength of the specific product in your hand. The same drug name is sold at several strengths, and paediatric liquids differ from adult ones. Read the strength off the label every time rather than reusing a volume that worked before.
Why small animals are the hard case
Rounding that is harmless for a 30 kg dog can be a large proportional change for a 3 kg cat. A quarter-tablet split by hand is not a quarter of the dose: tablets are rarely uniform, and scored tablets break unevenly. For small animals a compounded liquid measured with a syringe is the usual answer, and that comes from a pharmacy, not from a cutting board.
Species matter more than size. Cats metabolise several drug classes differently from dogs — they conjugate some compounds far more slowly — so a figure that is routine for a dog can be dangerous for a cat of the same weight. A dog figure is never a starting point for a cat.
Human medicines that are not scaled-down pet medicines
Some common household medicines are not safe for pets at any dose, which is a different problem from getting the arithmetic right:
Paracetamol / acetaminophen is dangerous to cats, which lack an enzyme pathway needed to clear it. Ibuprofen and naproxen are associated with gastrointestinal ulceration and kidney injury in both dogs and cats, and the margin between a tolerated and a toxic amount is narrow. Xylitol, used as a sweetener in some liquid medicines, chewing gums and sugar-free products, triggers a severe insulin response in dogs. Check the inactive ingredients, not only the active one.
If an animal has already swallowed any of these, that is an emergency call to a vet or a poison line, not a dosing question.
More answers
Can I use this instead of asking a vet?
No. This page explains the arithmetic and the units so you can follow and check what a veterinarian prescribes. The decision of whether to medicate, with what, and at what figure is a clinical one that depends on the animal’s history, other medicines and organ function.
Should I weigh the animal or estimate?
Weigh it. An estimate that is 20 per cent out carries straight through to the dose, and weight changes with age and illness. Home scales work for small animals if you weigh yourself holding them and subtract.
Does the dose change for a pregnant or elderly animal?
Often yes, and sometimes the drug changes rather than the figure. That is exactly the judgement this page cannot make for you.