All pharmacy calculators

58 calculators across 12 categories. Every one shows the complete formula, your substituted values, and each intermediate step.

Measurement & Conversions

Volume, weight, height, temperature, and mEq↔mmol interconversion.

Liquid (volume) conversions — Convert between metric and household/apothecary liquid measures using the equivalents conventionally applied in pharmacy practice.
Solid (weight) conversions — Convert between metric and avoirdupois/apothecary weight units, including grains.
Height & length conversions — Convert between inches, feet, centimetres, and metres for height-dependent calculations.
Temperature conversion (°F ↔ °C) — Convert between Fahrenheit and Celsius for fever assessment and product storage requirements.
Milliequivalents ↔ millimoles — Interconvert milliequivalents and millimoles using the ion's valence — 1:1 for monovalent ions, 1:0.5 for divalent ions.

Concentrations & Compounding

Strength, dilution, alligation, osmolarity, isotonicity, and weighing limits.

Percentage strength (w/v, v/v, w/w) — Convert between percentage strength, amount of solute, and total quantity for weight-in-volume, volume-in-volume, and weight-in-weight preparations.
Ratio strength — Convert between ratio strength (1 : X) and percentage strength for dilute preparations.
Parts per million (ppm) — Convert between parts per million, percentage strength, and ratio strength.
Specific gravity — Relate the weight and volume of a liquid through its specific gravity. Leave any one field blank to solve for it.
Dilution & concentration (Q₁C₁ = Q₂C₂) — Solve the dilution equation for any one of the four variables — leave the unknown blank.
Alligation (alternate) — Determine the proportions of a stronger and a weaker preparation needed to produce a desired intermediate strength.
Osmolarity (mOsmol/L) — Calculate the milliosmoles per litre contributed by a dissolved solute from its concentration, molecular weight, and number of dissociated particles.
Isotonicity — sodium chloride equivalent (E value) — Calculate a drug's sodium chloride equivalent and the amount of sodium chloride needed to make a solution isotonic.
Moles & millimoles — Convert between a mass of substance and the number of moles or millimoles it represents.
Milliequivalents from a salt weight — Convert between the weight of an electrolyte salt and the milliequivalents of ion it supplies.
Minimum weighable quantity & aliquot planner — Determine the smallest quantity a balance can weigh within an acceptable error, and plan an aliquot when the required amount falls below it.

Dosing & Body Metrics

BMI, ideal and adjusted body weight, body surface area, dosing-weight selection.

Body mass index (BMI) — Calculate body mass index from height and weight and classify it against the WHO categories.
Ideal body weight (Devine) — Calculate ideal body weight from height and sex using the Devine equations, with adjusted body weight and percentage of IBW alongside.
Adjusted body weight (AdjBW₀.₄) — Calculate adjusted body weight, the weight used for hydrophilic drugs such as aminoglycosides in obese patients.
Body surface area (Mosteller & Du Bois) — Calculate body surface area by the Mosteller equation, with the Du Bois equation shown for comparison.
Which weight to use for dosing — Determine whether a given drug should be dosed on total, ideal, or adjusted body weight for a specific patient, and return the resulting dosing weight.

Renal & Fluids

Creatinine clearance, maintenance fluids, infusion rates, volume status.

Creatinine clearance (Cockcroft–Gault) — Estimate creatinine clearance from age, sex, serum creatinine, and weight — the equation on which most renal dose adjustments in product labelling are based.
Maintenance fluid requirements — Estimate daily maintenance fluid requirements by the Holliday–Segar method, the >20 kg shorthand, and the adult 30–40 mL/kg/day range.
Infusion rate & drop factor — Convert between infusion rate in mL/hr, drops per minute, and total infusion time.
BUN : creatinine ratio — Calculate the ratio of blood urea nitrogen to serum creatinine, a supportive indicator of volume status and the pattern of renal impairment.

Nutrition Support

Enteral and parenteral calories, nitrogen balance, energy expenditure.

Enteral / dietary calories — Calculate total calories and macronutrient distribution from grams of carbohydrate, protein, and fat.
Parenteral nutrition calorie worksheet — Calculate total and per-component calories in a parenteral nutrition bag from the final dextrose and amino acid percentages and the lipid volume.
Nitrogen from protein — Convert between grams of protein and grams of nitrogen, and calculate the non-protein calorie to nitrogen ratio.
Total energy expenditure (TEE) — Calculate total energy expenditure from a basal energy expenditure multiplied by activity and stress factors.

Pharmacokinetics

Bioavailability, volume of distribution, clearance, half-life, loading dose.

Pharmacokinetic workspace (linked solver) — Enter any sufficient subset of pharmacokinetic parameters and derive the rest, with each result labelled by the relation used to obtain it.
Absolute bioavailability (F) — Calculate absolute bioavailability from the areas under the curve and doses of an extravascular and an intravenous administration.
Predicting drug concentrations — Predict a future concentration from a measured one, calculate the elimination rate constant from two measured concentrations, or find the time needed to reach a target concentration.
Loading dose — Calculate the dose needed to reach a target plasma concentration immediately, rather than waiting the five half-lives that maintenance dosing alone would require.

Acid-Base & Laboratory

Blood gas interpretation, anion gap, corrected values, ANC, MAP.

Arterial blood gas interpreter — Determine the primary acid–base disorder from pH, pCO₂, and bicarbonate, with a step-by-step account of how the conclusion was reached.
Anion gap — Calculate the serum anion gap, with optional correction for hypoalbuminaemia.
Corrected calcium for albumin — Adjust a total serum calcium for a low albumin, so that the result reflects the physiologically active fraction.
Corrected phenytoin for albumin (Sheiner–Tozer) — Adjust a total phenytoin concentration for hypoalbuminaemia, with a separate variant for significant renal impairment.
Absolute neutrophil count (ANC) — Calculate the absolute neutrophil count from the white cell count and the percentages of segmented neutrophils and bands.
Mean arterial pressure (MAP) — Calculate mean arterial pressure from systolic and diastolic blood pressure.

Physical Pharmacy

Henderson–Hasselbalch and degree of ionisation.

Henderson–Hasselbalch equation — Relate pH, pKa, and the ratio of conjugate species for a weak acid or weak base buffer system — solving for pH or for the ratio needed to reach a target pH.
Percentage ionisation — Calculate what fraction of a weak acid or weak base is ionised at a given pH, with an interactive curve showing how it changes across the physiological range.

Biostatistics & Outcomes

Risk, relative and absolute effect, NNT, odds and hazard ratios, cost-effectiveness.

2 × 2 table — risk, RR, RRR, ARR, NNT, OR — Enter a single 2 × 2 table and obtain every standard measure of effect at once: risk in each group, relative risk, relative and absolute risk reduction, number needed to treat or harm, and the odds ratio.
Hazard ratio — Calculate a hazard ratio from the hazard rates in the treatment and control groups.
Incremental cost-effectiveness ratio (ICER) — Calculate the additional cost per additional unit of effect when comparing two interventions.
Descriptive statistics — Calculate mean, median, mode, range, and standard deviation from a set of values.

Therapeutic Conversions

Dose equivalence within a drug class and between routes.

Corticosteroid equivalency — Convert between systemic corticosteroids on the basis of approximate glucocorticoid potency.
Statin dose equivalency — Convert between statins on the basis of approximately equivalent LDL-lowering effect.
Loop diuretic equivalency & route conversion — Convert between loop diuretics and between intravenous and oral routes.
Insulin product conversion — Convert between insulin products, applying the recognised 80% adjustments for NPH to glargine and for Toujeo to other glargine products.
IV ↔ PO route conversion — Convert a dose between intravenous and oral routes for drugs where the ratio is not one to one.
Aminophylline ↔ theophylline — Convert between aminophylline and theophylline using the 0.8 salt factor.
Calcium salt ↔ elemental calcium — Convert between the weight of a calcium salt and the elemental calcium it provides.
Potassium chloride 10% solution ↔ mEq — Convert between the volume of potassium chloride 10% oral solution and the milliequivalents of potassium it supplies, and find the equivalent number of tablets.
Lithium citrate syrup ↔ carbonate ↔ mEq — Convert between lithium citrate oral solution, lithium carbonate, and milliequivalents of lithium ion.

Diabetes & Lipids

Insulin initiation and adjustment, LDL estimation.

Insulin initiation & adjustment worksheet — Calculate a weight-based total daily insulin dose, split it into basal and mealtime components, and derive the insulin-to-carbohydrate ratio, correction factor, and a correction dose — all from a single weight entry.
LDL cholesterol (Friedewald equation) — Estimate LDL cholesterol from total cholesterol, HDL, and triglycerides — with a hard block above a triglyceride of 400 mg/dL, where the equation is invalid.

Public Health & Misc

Smoking history and sun-protection estimates.

Pack-year smoking history — Calculate cumulative tobacco exposure in pack-years, the standard measure used for lung cancer screening eligibility and risk assessment.
Sun protection — time to burn (SPF) — Estimate how long sun exposure can be extended by a sunscreen of a given SPF, and how much UVB it filters.