Pet Medication Dose Calculator

How to Use This Calculator

1. Enter your pet's weight in lbs, select species and medication.
2. The calculator shows the estimated dose in mg and standard frequency.
3. Use Liquid Suspension tab: enter dose rate and concentration (mg/mL) to get exact mL volume.
4. Use Professional for renal adjustment, contraindications, and clinical notes.
5. Always confirm doses with your veterinarian before administering.

Formula

Example

Frequently Asked Questions

• Why are pet medication doses calculated by weight? ▼
  Drug doses are calculated per kilogram of body weight because the pharmacokinetics — how a drug is absorbed, distributed, metabolized, and excreted — scale with body size. A 5-pound chihuahua and a 100-pound Labrador are the same species but require dramatically different absolute doses of the same drug to achieve the same therapeutic concentration in their blood and tissues. The target is typically a minimum inhibitory concentration (MIC) in the case of antibiotics — the blood level just high enough to suppress bacterial growth — or a therapeutic window for other drugs. Dosing too low results in treatment failure; dosing too high causes toxicity. Body weight is the practical proxy for this calculation because exact metabolic measurement is impractical in clinical settings. Most veterinary drug doses are expressed in mg per kg, which requires accurate weight measurement — this is why vets weigh patients at every visit. Weight-based dosing is also why treating pets with human medications based on guessing human "equivalents" is dangerous: a 500mg human amoxicillin capsule contains about 25mg/kg for a 20-kg dog, which is appropriate, but far too much for a 2-kg cat.
• Why is acetaminophen so dangerous for cats? ▼
  Acetaminophen (paracetamol, Tylenol) is acutely and often fatally toxic to cats due to a species-specific metabolic deficiency. Cats lack sufficient liver enzymes — specifically hepatic glucuronyl transferase — to conjugate and neutralize acetaminophen's toxic intermediate metabolite, NAPQI (N-acetyl-p-benzoquinone imine). In humans and dogs, NAPQI is quickly converted to harmless conjugates and excreted. In cats, NAPQI accumulates and attacks red blood cells and liver cells. The result is methemoglobinemia (red blood cells can no longer carry oxygen, turning chocolate-brown) and hepatic necrosis. A single regular-strength Tylenol tablet (325mg) can kill a cat. Clinical signs develop within 1-4 hours: facial and paw swelling, rapid breathing, brown mucous membranes, vomiting, and collapse. Emergency treatment with N-acetylcysteine (NAC) and supportive care can save cats if administered within hours of ingestion, but the window is narrow. This is why the first rule of pet medication safety is that no human pain reliever — acetaminophen, ibuprofen, naproxen, or aspirin — should ever be given to cats without explicit veterinary guidance, as all carry significant toxicity risks in felines.
• Can I give my dog human medications? ▼
  Some human medications are used in dogs at veterinary-prescribed doses, but self-medicating dogs with human drugs is genuinely dangerous and should never be done without veterinary guidance. The most common dangerous mistakes: ibuprofen (Advil) causes acute kidney failure and gastric ulcers in dogs at very low doses — a single 200mg tablet can be toxic in a small dog; naproxen (Aleve) is similarly toxic; pseudoephedrine (in decongestants) causes seizures and cardiac arrhythmias; xylitol (in many sugar-free products including some peanut butters and gummies) causes hypoglycemia and liver failure at extremely small amounts. Medications that dogs can sometimes safely receive with vet guidance include diphenhydramine (Benadryl) for allergies, some antacids, and certain antidiarrheal medications — but always with weight-appropriate dosing confirmed by a vet. The core problem is that dogs metabolize many drugs differently than humans — faster or slower, via different pathways — making human dosing irrelevant or dangerous. When in doubt, call your veterinarian or the ASPCA Animal Poison Control Center (888-426-4435) immediately rather than guessing.
• How do I measure liquid medications accurately for pets? ▼
  Accurate measurement of liquid pet medications requires an oral syringe — not a kitchen teaspoon or tablespoon, which can vary by 20-30% from their labeled volume. Oral syringes (without needles) are available free from most veterinary clinics and pharmacies and provide accurate mL measurements down to 0.1 mL. To draw up the correct volume, hold the syringe horizontally at eye level and read the bottom of the meniscus (the curved liquid surface) against the calibration marks. For very small doses (under 0.5 mL, common for cats and small dogs), extra care is needed because small measurement errors become large percentage errors — 0.1 mL error on a 0.3 mL dose is 33% of the dose. When possible, ask your vet to prescribe a concentration that gives a convenient volume — 1-3 mL is easy to measure accurately; 0.1 mL is very difficult. Shake suspensions thoroughly before drawing each dose as the active ingredient settles. Administer oral medications by placing the syringe between the cheek and gum, not directly down the throat, and allow the pet to swallow naturally to prevent aspiration. Refrigerated medications should be allowed to reach room temperature before dosing to reduce resistance to swallowing.
• What is the difference between dosing dogs and cats? ▼
  Cats are not small dogs — they have fundamentally different hepatic metabolism, renal physiology, and drug sensitivities that make feline dosing a distinct discipline from canine dosing. The most critical difference is glucuronidation capacity: cats have significantly reduced ability to conjugate drugs via glucuronic acid, meaning many drugs that dogs metabolize safely accumulate to toxic levels in cats. This is why acetaminophen, aspirin, and several common antibiotics (like amoxicillin-clavulanate at high doses) carry greater toxicity risk in cats. NSAIDs are another major difference: meloxicam is used at 0.1 mg/kg in dogs daily but only 0.05 mg/kg in cats, and even that dose carries renal toxicity risk with long-term use in felines. Cats also metabolize many drugs more slowly than dogs, meaning longer dosing intervals are appropriate — some drugs given twice daily in dogs are given once daily in cats. Body composition differs too: cats have proportionally less body fat, which affects volume of distribution for lipophilic drugs. Feline renal function also declines naturally with age faster than in dogs, making dose adjustments more frequently necessary in older cats. Always verify species-specific dosing with a veterinary reference like Plumb's Veterinary Drug Handbook rather than scaling from dog doses.

Related Calculators