Free NAPLEX & pharmacy calculation practice

RxMath Lab generates unlimited pharmacy calculation problems across all 19 high-yield topics, among them alligation, creatinine clearance, IV infusion rates, opioid conversions and TPN. Every problem is new, marked the moment you submit it, and comes with a worked solution that a PharmD wrote and checked.

Nothing here is a fixed question bank you can memorize your way through. The problems come from the formulas themselves, so the numbers change every time and the only way to get one right is to do the calculation. It costs nothing, it carries no advertising, and it does not ask you to make an account.

Practice every topic, mixed

Start here for a random problem from any of the 19 topics, or use the chips to lock the practice box to one. Every problem has a shareable link. Send one to a study partner and it opens the same question for them.

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Creatinine Clearance

Calculate the creatinine clearance (Cockcroft-Gault) for a 80-year-old male, 5'6" tall, weighing 52 kg, with a serum creatinine of 1.8 mg/dL. Select the appropriate body weight: use actual body weight if it is below IBW, adjusted body weight if it exceeds 125% of IBW, and IBW otherwise. Round your answer to the nearest whole number.

mL/min

Every problem has its own link. Hit Copy link to send a classmate this exact question, or to keep it for later.

Practice by topic

Each topic page has its own unlimited generator plus 10 fully worked problems to read through first.

Percentage & Ratio StrengthPercentage strength and ratio strength are two ways of saying how much drug is in a preparation.DilutionWhen you dilute a concentrated stock solution, the amount of drug stays constant while the volume increases, so the concentration falls.AlligationAlligation mixes two preparations of different strengths to get an intermediate strength.Milliequivalent (mEq), Millimole & MilliosmoleThese three units describe amounts of electrolytes.IV Infusion & Drip RateIV rate problems come in two flavors: gravity drip rates in drops per minute, and pump rates in mL/hr for weight-based infusions.Body Surface Area (BSA) & Chemo DosingMany chemotherapy and some pediatric drugs are dosed per square meter of body surface area (BSA).TPN & Nutrition CalculationTotal parenteral nutrition problems total the calories from dextrose, amino acids, and lipids.Isotonicity & E-ValueSolutions placed in the eye, nose, or bloodstream should be isotonic with body fluids (equivalent to 0.9% NaCl).Creatinine Clearance (Cockcroft-Gault)Creatinine clearance estimates kidney function to guide renal dose adjustments.PharmacokineticsCore PK calculations connect dose, concentration, and the body's handling of a drug.Bioavailability (F)Absolute bioavailability compares how much drug reaches the systemic circulation from an oral dose versus an IV dose (which is 100% by definition).Insulin Day Supply & SwitchingInsulin calculations at the pharmacy come down to two things: day supply, and switching between basal products.Opioid Conversion & MMEOpioid math converts between opioids and routes using an equianalgesic table anchored to 30 mg of oral morphine.Days Supply CalculationDays supply is how long a dispensed quantity lasts, which is what insurance billing and refill timing are calculated from.Weight-Based (mg/kg) DosingMany drugs, especially in pediatrics, are dosed by body weight in mg/kg.Reconstitution & Powder VolumeReconstituting a powdered drug adds diluent to reach a target concentration, but the dry powder occupies space of its own.Specific GravitySpecific gravity relates a liquid's weight to its volume, so you can convert between grams and milliliters.Clinical Lab CalculationSeveral bedside calculations adjust or interpret a lab value before you can act on it.Dispensing QuantityMost pharmacy calculations round to the nearest value.

Keep these open while you work

Three reference pages, each built from the same generators as the practice problems.

Formula sheetEvery formula on the site, what each one is for, and a worked example of each. Common mistakesThe specific setup error built into each topic, with the example that shows it biting. Worked examplesOne fully worked problem for every question type the site generates, all 42.

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