Pharmacy Calculations, Sig Codes and Conversions
Calculation questions test formulas, ratios, proportions, conversions, Sig codes, abbreviations, terminology, days supply, quantity, dose, concentration, and dilutions.
How to study for the PTCE
Build every answer around medication safety: identify the drug, law, risk, calculation, product, and pharmacist-escalation point.
Core concepts
Concept 1
Calculation questions should be solved by identifying units, formula, and desired answer before doing arithmetic.
Exam cue: Write units and desired output first.
Concept 2
Sig codes, abbreviations, and terminology translate directions into quantity and days supply.
Exam cue: Convert before multiplying or dividing.
Concept 3
Ratios, proportions, conversions, concentration, and dilutions are recurring PTCE math patterns.
Exam cue: For days supply, connect directions, quantity dispensed, and daily use.
Risk pitfalls and guardrails
Mixing milligrams, grams, milliliters, and units.
Guardrail: Avoid answers that skip pharmacist review, ignore controlled-substance or DSCSA rules, mix units, or return questionable product to stock.
Reading b.i.d. or t.i.d. incorrectly.
Guardrail: Avoid answers that skip pharmacist review, ignore controlled-substance or DSCSA rules, mix units, or return questionable product to stock.
Calculating quantity without checking duration.
Guardrail: Avoid answers that skip pharmacist review, ignore controlled-substance or DSCSA rules, mix units, or return questionable product to stock.
Memory anchors
Ratio
A ratio compares two quantities.
Proportion
A proportion states that two ratios are equal.
Conversion
Conversion changes a value from one unit to another.
Sig Code
Sig codes abbreviate prescription directions.
Days Supply
Days supply equals quantity dispensed divided by amount used per day.
Dose
Dose is the amount of medication taken at one time.
Concentration
Concentration is amount of drug per volume or unit.
Dilution
Dilution lowers concentration by adding diluent.
Roman Numeral
Roman numerals can appear in prescription quantities or directions.
Medical Terminology
Medical terminology supports accurate interpretation of orders.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A prescription reads: amoxicillin 500 mg, take one capsule three times daily for 10 days. How many capsules should be dispensed?
A patient receives 60 tablets with directions to take one tablet twice daily. What is the days supply?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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