How We Calculate Dosage Ranges
Transparency is central to our mission. Here is exactly how we arrive at every number on PetDosageChart.
Our Sources
Every dosage range on PetDosageChart is derived from established veterinary pharmacology references. We cross-reference multiple sources to ensure accuracy:
Plumb's Veterinary Drug Handbook
The gold standard for veterinary drug dosing. Now in its 10th edition, Plumb's provides evidence-based dosage ranges, contraindications, and drug interaction data for hundreds of veterinary medications. This is our primary reference for all dose ranges.
Merck Veterinary Manual
A comprehensive, peer-reviewed resource covering pharmacology, disease management, and drug safety in animals. We use Merck as a secondary verification for dosage ranges and as a source for contraindication and drug interaction data.
DailyMed (U.S. National Library of Medicine)
DailyMed provides FDA-approved labeling for animal drugs. We reference DailyMed for official product labels, available tablet sizes, and formulation details to ensure our calculator reflects real-world products.
Peer-Reviewed Veterinary Literature
For newer medications or off-label uses, we consult published studies from journals such as the Journal of Veterinary Internal Medicine (JVIM) and the Journal of the American Veterinary Medical Association (JAVMA).
The Math
Veterinary dosing is calculated on a milligrams per kilogram (mg/kg) basis. Here is the formula our calculator uses:
Dose (mg) = Weight (kg) × Dose Rate (mg/kg)
Step 1: Convert weight. If the pet's weight is in pounds, divide by 2.205 to get kilograms.
Step 2: Calculate dose range. Multiply the weight in kg by the low, standard, and high dose rates from our references.
Step 3: Find the closest tablet. Match the calculated dose to the nearest available tablet size (see below).
For example, a 25 lb dog (11.3 kg) needing diphenhydramine at 2 mg/kg would require 22.7 mg. The closest available tablet is 25 mg, so the calculator suggests one 25 mg tablet.
Closest Tablet Logic
Most pet medications come in fixed tablet sizes. Our calculator does not just display a raw milligram number — it also suggests the most practical tablet combination:
- We maintain a list of commercially available tablet sizes for each medication (e.g., 25 mg and 50 mg for diphenhydramine).
- The calculator finds the single tablet or combination of tablets that gets closest to the calculated dose without exceeding the high-range limit.
- When in doubt, we round down rather than up — it is safer to slightly under-dose than to overdose.
- For medications available in liquid form, we display the exact milliliter measurement using the product's concentration.
Review Process
Accuracy is non-negotiable for a dosage reference site. Our review process includes:
- Initial data entry: Dosage ranges are extracted from primary references with full citations.
- Cross-referencing: Every entry is verified against at least two independent sources.
- Veterinary review: A licensed veterinarian reviews dosage data for clinical accuracy and real-world applicability.
- Calculator testing: We test edge cases (very small breeds, very large breeds, maximum daily doses) to ensure the math is correct.
- Ongoing monitoring: We watch for FDA safety alerts, label changes, and new research that may affect dosage recommendations.
Transparency note: We are not a veterinary practice. Our dosage information is curated from published references and reviewed for accuracy, but it does not replace professional veterinary advice. Always consult your vet before medicating your pet.
Update Log
We maintain a log of significant data updates for transparency.
| Date | Update |
|---|---|
| 2026-03-21 | Added methodology page with full source documentation and review process details. |
| 2026-03-08 | Initial launch with dog medications (Tier 1–5) and cat medications. All entries cross-referenced against Plumb's and Merck. |
Report an Error
If you spot an incorrect dosage, outdated information, or any other error, we want to know. Accurate information saves lives.
Help us improve: If you are a veterinarian, veterinary technician, or pharmacist and you notice an issue, please reach out. We take every correction seriously and will update our data promptly.
Email corrections to: corrections@petdosagechart.com
Please include the medication name, the error you found, and a reference source if possible.