PEBC® Pharmacy Calculations: Formula Sheet, Canadian Units and Practice Questions

Calculations on the PEBC® Pharmacist Qualifying Examination Part I sit mostly inside Distribution (20% of Part I under the Blueprint Ver. 03-2026) and inside clinical cases, rather than in a separate section, where a dose, a renal function estimate or a quantity to dispense decides the right answer. They are rarely the hardest questions on the exam, but they are the easiest to lose under time pressure through a unit slip.

This page shows exactly what PEBC's on-screen reference sheet contains, the formulas it leaves out that you still need to know, the Canadian SI units that catch out international graduates, and 8 original worked questions. Set a 2-minute limit per question when you practise; if a calculation is taking longer, flag it and come back.

Last reviewed October 19, 2026 · Based on the Pharmacist Qualifying Examination Blueprint, Ver. 03-2026

What PEBC gives you on exam day

Part I is closed-book. PEBC says no aids are permitted other than the on-screen calculator and formula sheet it provides. The calculator has basic and scientific modes; you cannot bring a physical calculator to a test centre or to a remotely proctored sitting. Molecular and atomic weights are supplied when a question needs them, and most values and answers are in SI (metric) units.

PEBC publishes the reference sheet in advance. The current version (dated March 1, 2024) contains only the formulas below. Look at it before exam day so you know where everything is, and read the official reference sheet PDF to confirm it has not changed.

PEBC Pharmacist Qualifying Exam Part I reference sheet (version dated March 1, 2024)
FormulaWhat it is for
t½ = 0.693 / keHalf-life from the elimination rate constant
Css = R0 / (ke x Vd)Steady-state concentration during a constant infusion
Cpk = D / [Vd (1 - e^(-ke x t))]Peak concentration at steady state with repeated IV bolus doses (here t is the dosing interval)
C1 = C0 x e^(-ke x t)Concentration after time t (first-order elimination)
CrCl (male) = (140 - age) x actual body weight (kg) x 1.2 / serum creatinine (µmol/L)Cockcroft-Gault creatinine clearance in mL/min
CrCl (female) = 0.85 x CrCl (male)Female adjustment to the same equation
BMI = weight (kg) / height² (m²)Body mass index

Formulas to know from memory

Even for the formulas on the sheet, you need to recognize which one a case is asking for and set it up quickly. The rows marked "on the sheet" are given to you; the rest are not.

Core pharmacy calculation formulas
CalculationFormulaWatch out for
Weight-based doseDose (mg) = dose (mg/kg) x weight (kg)Per dose or per day? Divide a daily dose by the number of doses. Convert pounds with 1 kg = 2.2 lb.
Volume of a liquid doseVolume (mL) = dose (mg) / concentration (mg/mL)Convert the label first, e.g. 400 mg/5 mL = 80 mg/mL.
Creatinine clearance (Cockcroft-Gault, on the sheet)CrCl (mL/min) = (140 - age) x actual body weight (kg) x 1.2 / SCr (µmol/L). Females: x 0.85Canada reports serum creatinine in µmol/L. Do not use the US mg/dL version (72 x SCr in the denominator). Some Canadian references write the constants as 1.23 and 1.04; the result is almost the same.
Ideal body weight (Devine)Males: 50 kg + 2.3 kg per inch over 5 feet. Females: 45.5 kg + 2.3 kg per inch over 5 feet1 inch = 2.54 cm. Use the weight the question or monograph specifies.
Body surface area (Mosteller)BSA (m²) = square root of [height (cm) x weight (kg) / 3600]Used for many chemotherapy doses (mg/m²).
DilutionC1 x V1 = C2 x V2Keep both concentrations in the same units (% w/v or mg/mL).
AlligationParts of stronger = desired - weaker. Parts of weaker = stronger - desiredDesired strength must sit between the two you are mixing.
Percentage strength% w/v = g per 100 mL. % w/w = g per 100 g. % v/v = mL per 100 mL1% w/v = 10 mg/mL.
Ratio strength1:1000 = 1 g in 1000 mL = 1 mg/mLEpinephrine 1:1000 is 1 mg/mL; 1:10,000 is 0.1 mg/mL.
Millimolesmmol = mg / molecular weight. For monovalent ions, mmol = mEqmmol is the usual unit in Canada, but mEq still appears. mEq = mmol x valence, so for calcium or magnesium 1 mmol = 2 mEq.
Infusion ratemL/h = volume (mL) / time (h). Drops/min = mL/h x drop factor (gtt/mL) / 60Check whether the question wants mL/h or drops per minute.
Quantity and days' supplyQuantity = dose per day x days. Days' supply = quantity / dose per dayAdd priming doses for pens, and round up to whole units (pens, tablets) or to packages only if the question asks.

Canadian SI units that trip up international graduates

Canadian labs, guidelines and PEBC cases use SI units. If you trained with US or other references, convert your mental reference ranges before the exam rather than during it.

Common conversions (approximate factors)
Lab valueCanadian unitTo convert from conventional units
Serum creatinineµmol/Lmg/dL x 88.4
Glucosemmol/Lmg/dL / 18
Total, LDL and HDL cholesterolmmol/Lmg/dL / 38.67
Triglyceridesmmol/Lmg/dL / 88.57
Hemoglobing/Lg/dL x 10
A1C% (also reported in mmol/mol)Canadian targets are usually written in %, e.g. 7.0% or less

A method that survives exam pressure

  1. Read the question line first so you know what unit the answer must be in.
  2. Write down each number from the stem with its unit.
  3. Convert everything to the units of the answer before you calculate.
  4. Set up the whole calculation, then use the calculator once rather than rounding at every step.
  5. Sanity-check the result: is it a dose or volume a pharmacist would actually dispense?
  6. Round only at the end, and the way the question asks (to a measurable volume, to whole tablets or to whole packages).

Practice questions

Original questions written for this page. Answer each one before you open the explanation.

Question 1Calculations: paediatric dosing
Providing Care: Distribution

A 4-year-old child weighing 16 kg has uncomplicated acute otitis media and is prescribed amoxicillin 90 mg/kg/day, divided twice daily, for 5 days. The pharmacy stocks amoxicillin suspension 400 mg/5 mL.

What is the minimum volume of suspension needed to complete the course?

  1. A.45 mL
  2. B.75 mL
  3. C.90 mL
  4. D.135 mL
  5. E.180 mL
Show answer and explanation

Answer: C

16 kg x 90 mg/kg/day = 1440 mg/day, so 720 mg per dose. The suspension is 400 mg/5 mL = 80 mg/mL, so each dose is 720 / 80 = 9 mL. Two doses a day for 5 days is 9 x 2 x 5 = 90 mL.

Why the other options are wrong

  • A:This is one 9 mL dose a day for 5 days, forgetting the daily dose is divided twice daily.
  • B:This uses 75 mg/kg/day, not the 90 mg/kg/day prescribed.
  • D:This gives the 9 mL dose three times a day instead of twice.
  • E:This is a 10-day course. The prescription is for 5 days, which matches Canadian guidance for uncomplicated otitis media in children 2 years and older; 10 days is for children 6 to 23 months.

Reference: Canadian Paediatric Society, Management of acute otitis media in children six months of age and older (2016, reaffirmed 2024): amoxicillin 75 to 90 mg/kg/day divided twice daily; 5 days for most children 2 years and older.

Question 2Calculations: renal function
Providing Care: Clinical Care

A 78-year-old woman weighing 60 kg has a serum creatinine of 110 µmol/L. Her prescriber asks for her estimated creatinine clearance to adjust a renally cleared drug.

Using the Cockcroft-Gault equation on the PEBC reference sheet, what is her estimated creatinine clearance?

  1. A.0.4 mL/min
  2. B.29 mL/min
  3. C.34 mL/min
  4. D.41 mL/min
  5. E.62 mL/min
Show answer and explanation

Answer: C

Male value first: (140 - 78) x 60 x 1.2 / 110 = 4464 / 110 = 40.6 mL/min. For a female, multiply by 0.85: 40.6 x 0.85 = about 34 mL/min.

Why the other options are wrong

  • A:This plugs a µmol/L creatinine into the US mg/dL version of the equation (72 x SCr in the denominator). The units do not match.
  • B:This applies the 0.85 female adjustment twice.
  • D:This is the male value. She is female, so multiply by 0.85.
  • E:This is just 140 minus her age, with no weight or creatinine in the calculation.

Reference: PEBC Pharmacist Qualifying Examination Part I reference sheet (March 2024); Cockcroft DW, Gault MH. Nephron. 1976.

Question 3Calculations: infusion rate
Providing Care: Distribution

Vancomycin 1 g in 250 mL normal saline is to be infused over 2 hours using a gravity administration set with a drop factor of 20 gtt/mL.

What drip rate should be set?

  1. A.21 gtt/min
  2. B.42 gtt/min
  3. C.63 gtt/min
  4. D.125 gtt/min
  5. E.167 gtt/min
Show answer and explanation

Answer: B

250 mL over 2 hours = 125 mL/h. 125 mL/h x 20 gtt/mL / 60 min/h = 41.7, rounded to 42 gtt/min.

Why the other options are wrong

  • A:This uses a 10 gtt/mL drop factor instead of 20.
  • C:This uses a 30 gtt/mL drop factor instead of 20.
  • D:125 is the rate in mL/h, not drops per minute.
  • E:This runs the full 250 mL over 30 minutes at 20 gtt/mL, ignoring the 2-hour infusion time.

Reference: Worked arithmetic.

Question 4Calculations: dilution
Providing Care: Distribution

A pharmacist needs to prepare 200 mL of a 0.5% w/v solution from a 4% w/v stock solution.

How much of the stock solution is needed?

  1. A.8 mL
  2. B.25 mL
  3. C.40 mL
  4. D.50 mL
  5. E.175 mL
Show answer and explanation

Answer: B

C1 x V1 = C2 x V2, so 4% x V1 = 0.5% x 200 mL. V1 = 100 / 4 = 25 mL of stock, made up to 200 mL with diluent.

Why the other options are wrong

  • A:This divides 4 by 0.5 to get the dilution factor (8) and stops there. The factor is 8, but the volume is 200 / 8 = 25 mL.
  • C:This would give a 0.8% solution.
  • D:This would give a 1% solution.
  • E:175 mL is the volume of diluent to add, not the volume of stock.

Reference: Worked arithmetic.

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Question 5Calculations: anaphylaxis
Providing Care: Clinical Care

A 25 kg child is in anaphylaxis at a pharmacy vaccination clinic. The pharmacist has epinephrine 1 mg/mL (1:1000) ampoules and will give 0.01 mg/kg intramuscularly.

What volume should be drawn up?

  1. A.0.025 mL
  2. B.0.15 mL
  3. C.0.25 mL
  4. D.0.5 mL
  5. E.2.5 mL
Show answer and explanation

Answer: C

0.01 mg/kg x 25 kg = 0.25 mg. At 1 mg/mL, that is 0.25 mL, below the 0.5 mg maximum single dose. When the weight is known, dose by weight; this matches the 21 to 25 kg row of the Canadian Immunization Guide dosing table. Never delay epinephrine: if only an auto-injector is at hand, use it.

Why the other options are wrong

  • A:This treats 1:1000 as 10 mg/mL. Ratio strength 1:1000 means 1 g in 1000 mL, which is 1 mg/mL.
  • B:0.15 mg is the fixed dose in a junior auto-injector. It is not the result of the weight-based calculation the question asks for.
  • D:0.5 mg is the maximum single dose, not the dose for a 25 kg child.
  • E:This uses the 1:10,000 (0.1 mg/mL) concentration, which is not what the pharmacist has.

Reference: Canadian Immunization Guide, Anaphylaxis and other acute reactions following vaccination (Public Health Agency of Canada).

Question 6Calculations: alligation
Providing Care: Distribution

A prescription calls for 100 g of a 5% ointment. The pharmacy has the same ointment in 10% and 2% strengths.

How many grams of the 10% ointment are needed?

  1. A.30 g
  2. B.37.5 g
  3. C.50 g
  4. D.60 g
  5. E.62.5 g
Show answer and explanation

Answer: B

By alligation, the 10% gets 5 - 2 = 3 parts and the 2% gets 10 - 5 = 5 parts, 8 parts in total. 10% ointment = 3/8 x 100 g = 37.5 g; 2% ointment = 62.5 g. Check: (37.5 x 10% + 62.5 x 2%) / 100 = 5%.

Why the other options are wrong

  • A:This takes 3/10 of 100 g, using the wrong total number of parts.
  • C:Equal amounts would give 6%, the simple average of 10% and 2%.
  • D:This would give 6.8%.
  • E:This is the amount of the 2% ointment, not the 10%.

Reference: Worked arithmetic.

Question 7Calculations: quantity to dispense
Providing Care: Distribution

A patient injects insulin glargine 32 units once daily using 3 mL prefilled pens of 100 units/mL. Before each injection the patient does a 2-unit safety test, as the pen instructions direct.

How many pens are needed for a 90-day supply?

  1. A.9 pens
  2. B.10 pens
  3. C.11 pens
  4. D.15 pens
  5. E.31 pens
Show answer and explanation

Answer: C

Each pen holds 3 mL x 100 units/mL = 300 units. Daily use is 32 + 2 = 34 units, so 90 days needs 3060 units. 3060 / 300 = 10.2, so 11 pens.

Why the other options are wrong

  • A:This ignores the 2-unit safety test and then rounds 9.6 pens down. Always round a supply up, or the patient runs out.
  • B:This ignores the 2-unit safety test (32 x 90 = 2880 units = 9.6 pens, rounded up to 10).
  • D:This is three boxes of five, rounding to boxes when the question asks for pens.
  • E:This treats each pen as holding 100 units. A 3 mL pen at 100 units/mL holds 300 units.

Reference: Worked arithmetic. 2-unit safety test before each injection as in Sanofi Canada's Lantus SoloSTAR instructions for use.

Question 8Calculations: millimoles
Knowledge and Expertise

A patient is prescribed potassium chloride 1.5 g daily as extended-release tablets. Atomic weights: K 39.10, Cl 35.45 (KCl 74.55 g/mol).

How many millimoles of potassium is this per day?

  1. A.0.02 mmol
  2. B.13 mmol
  3. C.20 mmol
  4. D.38 mmol
  5. E.112 mmol
Show answer and explanation

Answer: C

1500 mg / 74.55 mg/mmol = 20.1 mmol of KCl. Each mmol of KCl releases 1 mmol of potassium, so about 20 mmol (also 20 mEq, since potassium is monovalent).

Why the other options are wrong

  • A:This divides 1.5 g by 74.55, which gives 0.020 moles. Convert to milligrams first, or multiply by 1000: 0.020 mol = 20 mmol.
  • B:This uses 1 g instead of 1.5 g.
  • D:This divides by the atomic weight of potassium (39.10) instead of the molecular weight of KCl. The 1.5 g is the weight of the whole salt.
  • E:This multiplies 1.5 by 74.55 instead of dividing.

Reference: Worked arithmetic. Molecular weight of KCl 74.55 g/mol.

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Frequently asked questions

Does PEBC give you a formula sheet?

Yes. Part I includes an on-screen reference sheet with half-life and steady-state pharmacokinetic formulas, Cockcroft-Gault creatinine clearance and BMI, and molecular weights are supplied when needed. PEBC publishes the sheet in advance. It does not include ideal body weight, BSA, dilution or alligation formulas.

Can I bring my own calculator to the PEBC exam?

No. A physical calculator is prohibited at test centres and in remotely proctored sittings. You use the on-screen calculator, which has basic and scientific modes. Practise with a similar on-screen calculator so the layout does not slow you down.

How many calculation questions are on PEBC Part I?

PEBC does not publish a count. Calculations are not a separate section of the blueprint; they sit inside Distribution and clinical cases, so expect them spread through the exam rather than grouped together.

Which creatinine clearance formula does the PEBC exam use?

PEBC's reference sheet uses Cockcroft-Gault in SI units with actual body weight: (140 - age) x weight in kg x 1.2, divided by serum creatinine in µmol/L, then x 0.85 for females. In exam calculations, use a different weight only if the question tells you to. In practice, weight selection (for example in obesity) follows the drug monograph.

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PharmaStudyAI is an independent study tool. It is not affiliated with, endorsed by, or connected to the Pharmacy Examining Board of Canada (PEBC®). PEBC® is a registered trademark of the Pharmacy Examining Board of Canada. Content is for exam study only and is not a substitute for clinical judgement or current product monographs.