NAPLEX Calculations Practice Questions
Calculations are subdomain 1.C of the NAPLEX outline and turn up inside patient cases too. Most are fill-in-the-blank: you type a number rounded the way the question says, using the on-screen calculator.
225 questions in 6 hours across all five content domains, with an explanation for every answer and a score by domain.
Or try the free calculations drillA community water system is fluoridated at 0.7 ppm. Which concentration is equivalent?
Formulas the NAPLEX expects you to know
| Calculation | Formula |
|---|---|
| Creatinine clearance (Cockcroft-Gault) | CrCl (mL/min) = [(140 − age) × weight (kg)] ÷ (72 × SCr in mg/dL), × 0.85 for femalesRead the question for which weight to use (actual, ideal or adjusted). |
| Ideal body weight (Devine) | Men 50 kg + 2.3 kg per inch over 5 feet; women 45.5 kg + 2.3 kg per inch over 5 feetAdjusted body weight = IBW + 0.4 × (actual − IBW). |
| Body surface area (Mosteller) | BSA (m²) = √[height (cm) × weight (kg) ÷ 3600]Used for many chemotherapy doses. |
| Milliequivalents | mEq = mg × valence ÷ molecular weightQuestions give the molecular weight; KCl has valence 1, CaCl₂ valence 2. |
| Osmolarity | mOsmol/L = (g/L ÷ MW) × number of particles × 1000NaCl dissociates into 2 particles, dextrose into 1. |
| Dilution | C₁ × V₁ = C₂ × V₂Also works for percentage and ratio strengths. |
| Alligation | Parts of each = distance of the other strength from the desired strengthFor mixing a stronger and a weaker preparation. |
| Infusion rate | mL/h = dose per hour ÷ concentration; gtt/min = mL/h × drop factor ÷ 60Watch mcg/kg/min units. |
| Pharmacokinetics | kₑ = ln(C₁/C₂) ÷ Δt; t½ = 0.693 ÷ kₑ; loading dose = Cp × VdVd in L/kg times weight. |
| Biostatistics | ARR = CER − EER; RRR = ARR ÷ CER; NNT = 1 ÷ ARR (rounded up)Sensitivity = TP ÷ (TP + FN); specificity = TN ÷ (TN + FP). |
The outline lists nine calculation areas: patient parameters and lab measures, quantities to dispense or administer, rates of administration, dose conversions, concentrations and ratio strengths with osmolarity, compounding quantities, nutrition, biostatistical and pharmacoeconomic measures, and pharmacokinetic parameters.
Then sit all 225 questions under the clock
225 questions in 6 hours across all five content domains, with an explanation for every answer and a score by domain.
Or try the free calculations drillCommon questions
How many calculation questions are on the NAPLEX?
NABP does not publish a count. Calculations are subdomain 1.C of Foundational Knowledge for Pharmacy Practice, which is 25% of the 200 scored questions, and calculations also appear inside patient scenarios.
Can you use a calculator on the NAPLEX?
Yes. An on-screen calculator works in scientific or five-function mode, and NABP says many calculations require the scientific mode. Personal calculators are not allowed.
How do you enter a NAPLEX calculation answer?
Fill-in-the-blank questions take a typed number. The question states the rounding, for example “round the final answer to the nearest WHOLE number,” and you enter only the number.
More NAPLEX guides
Source: NABP, NAPLEX Content Outline (effective May 1, 2025). Original independent practice; NAPLEX is a registered trademark of NABP. Not affiliated with or endorsed by NABP.