Methodology & sources

PharmCalc version 1.2.0 · released 2026-07-26 · 58 calculators

Design principle: show the work

PharmCalc's central design commitment is transparency. Every calculator displays the complete formula, the values you entered substituted into it, each intermediate step, and the source and rationale for the algorithm. Nothing is computed behind a curtain.

The point is that you can audit any number this tool produces rather than trusting it.

Sources and citation policy

Every calculator cites primary sources — the original derivation paper where one exists, current professional-society guidelines, USP general chapters, and FDA-approved labelling. Every constant, conversion factor, equivalency table, and reference range in the application lives in a single versioned data file with a citation attached to each entry, rather than being scattered through the code.

Formulae, physical constants, and conversion factors are facts and are not subject to copyright. All explanatory text, worked examples, clinical pearls, and limitations in PharmCalc are original writing. No reference work's prose, table layout, or organisational structure has been reproduced.

Where conventions differ

Pharmacy practice uses rounded conventional equivalents in several places — 1 fluid ounce as 30 mL, 1 kg as 2.2 lb, 1 grain as 65 mg — that differ from the exact SI values. PharmCalc uses the practice conventions, because they are what dosing devices and product labels are built around, and flags the exact value alongside wherever the difference could matter.

Deliberate blocks

Several calculators refuse to produce a result rather than return a misleading one. This is a design decision: a wrong number presented confidently is more dangerous than no number.

• Friedewald above a triglyceride of 400 mg/dL — the VLDL assumption fails; non-HDL cholesterol is offered instead.
• Alligation where the desired strength lies outside the bracketing pair — the problem has no solution.
• Ideal body weight below 152.4 cm (5 feet) — the Devine equation is undefined there and would return an unvalidated extrapolation.
• Any zero or negative denominator, and inconsistent input combinations, throughout.

Coverage

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