Methodology · Sources & Math
How we calculate dosage ranges.
Each calculator applies the lower, standard, and upper mg/kg values stored in that medication's structured record. The page lists the source names attached to the record and separates that sourcing from independent veterinary review.
PetDosageChart is a software-led publisher, not a veterinary practice. A page is independently DVM-reviewed only when it shows a named reviewer byline and review date.
01
Our sources
Medication records name established veterinary references. Most records list Plumb's and the Merck Veterinary Manual; official label searches are linked separately when useful. Source names are currently recorded at title level rather than as passage-level page or label citations.
Plumb's Veterinary Drug Handbook
A widely used veterinary pharmacology reference and the primary source name recorded for most medication entries on this site. Access to the underlying text may require a subscription or book.
Merck Veterinary Manual
A veterinary reference named in many medication records. We link to the official resource, but do not claim that every sentence or numeric value on a page has a matching Merck passage.
DailyMed (U.S. National Library of Medicine)
DailyMed provides current U.S. product labels. Medication pages link to a search for the generic drug so readers can check formulations and warnings. A human or animal label does not by itself validate an off-label veterinary use.
What a source listing does not mean
It does not mean PetDosageChart has performed a clinical review, chosen the right indication, or verified a dose for an individual pet. Those judgments belong to a veterinarian who knows the animal and the exact product being considered.
02
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 the reference range. Multiply the weight in kg by the recorded lower, standard, and upper mg/kg values.
Step 3: Show a tablet comparison. Compare the arithmetic result with recorded tablet sizes; this is not a dispensing instruction.
For example, 25 lb converts to about 11.3 kg. Multiplying 11.3 kg by a recorded 2 mg/kg reference produces 22.7 mg. That result explains the math only; it does not establish that diphenhydramine is appropriate or that a particular tablet should be given.
03
Tablet comparison logic
When a record includes common tablet sizes, the calculator displays a mathematical comparison. The limits are important:
- The record stores commonly encountered tablet strengths; a specific product may use different strengths or formulations.
- The calculator rounds to a nearby quarter-tablet equivalent. It does not inspect the product label or guarantee that splitting is permitted.
- The comparison can be above or below the standard arithmetic result. It must not be treated as a recommendation to round a dose.
- The calculator does not choose a liquid concentration, route, release type, or veterinary product. Confirm all of those with a veterinarian or pharmacist.
04
Review process
Our editorial process separates software checks, source transparency, and independent clinical review:
- Structured record: Each medication record contains mg/kg values, frequency, forms, cautions, interactions, and source names.
- Software testing: Automated tests cover unit conversion, dose multiplication, small-dose precision, invalid inputs, and generated-page indexability.
- Independent DVM review (pending page by page): A completed review adds a confirmed veterinarian's byline and review date. Without both, the page is not DVM-reviewed.
- Corrections and updates: The editorial team maintains the software and content records, documents material changes, and accepts cited corrections.
Which pages are reviewed?
Independent DVM review is being rolled out page by page. A page has been reviewed only when it shows a named reviewer byline and a last-reviewed date at the top; pages without that byline are based on a structured source record but not yet DVM-reviewed. We do not list a reviewer without confirmed credentials, written consent, and a completed review.
We are not a veterinary practice, and no page here replaces professional veterinary advice. Always consult your vet before medicating your pet.
05
Update log
We maintain a log of significant data updates for transparency.
| Date | Update |
|---|---|
| 2026-07-22 | Clarified source-record limitations, DVM review status, small-dose precision, and tablet-comparison wording. |
| 2026-03-21 | Added methodology page with full source documentation and review process details. |
| 2026-03-08 | Initial launch with structured dog and cat medication records and weight-based calculator pages. |
06
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.