ProReckoner's pharmacy calculators are built for pharmacists, pharmacy technicians and dispensary staff. Tools cover everyday dispensing tasks (days supply, dose frequency, tablet splitting), compounding calculations (alligation, dilution, reconstitution), clinical pharmacy (Cockcroft-Gault creatinine clearance, renal dose adjustment, BSA) and pharmacy business tools (markup, dispensing fee estimator, cost per day). All tools reference current Australian and international pharmacy guidelines.
Dispensing
3 toolsDays Supply Calculator
Total days supply from quantity dispensed, dose amount and daily frequency. Flags short courses and unusually large supplies.
Days supply = (Qty ÷ Dose per admin) ÷ Doses per day
Example: 60 tablets, 1 tablet BD → (60÷1)÷2 = 30 daysLiquid: 200 mL, 5 mL TDS → (200÷5)÷3 = 13.3 days
Dose Frequency Converter
Convert total daily dose to per-administration dose for any frequency — OD, BD, TDS, QID, q4h through to weekly.
Dose per admin = Total daily dose ÷ Doses per day
Doses per day: OD=1 · BD=2 · TDS=3 · QID=4 · q4h=6 · q6h=4 · q8h=3 · q12h=2
Tablet Splitting Checker
Determines if a prescribed dose can be achieved by splitting available tablets. Flags unsafe splits and modified-release forms.
Never split: Modified-release, enteric-coated, capsules, sublingual, buccal
Caution: Unscored tablets — dose uniformity cannot be guaranteed
Compounding & Concentration
3 toolsConcentration & Dilution
C₁V₁ = C₂V₂ dilution solver — enter any three values to find the fourth. Also calculates % w/v concentration.
C₁V₁ = C₂V₂
Example: Dilute 10 mg/mL stock to 2 mg/mL in 50 mL totalV₁ = (2 × 50) ÷ 10 = 10 mL stock + 40 mL diluent
% w/v = (mass g ÷ volume mL) × 100
2 g in 100 mL = 2% w/v = 20 mg/mL
Alligation Calculator
Find the mixing ratio of two concentrations to achieve a target concentration. Enter all three percentages and optionally the total volume needed.
Parts of high = Desired % − Lower %
Parts of low = Higher % − Desired %
Example: Mix 10% with 2% to make 5%:Parts of 10% = 5−2 = 3 · Parts of 2% = 10−5 = 5 · Ratio = 3:5
For 200 mL: 75 mL of 10% + 125 mL of 2%
Reconstitution Volume
Volume to withdraw after reconstituting a powdered vial. Accounts for displacement volume stated on the label.
Total volume = Diluent added + Displacement volume
Concentration = Vial mg ÷ Total volume
Volume to give = Ordered dose ÷ Concentration
Example: 500 mg vial, 9.6 mL diluent, 0.4 mL displacementTotal vol = 10 mL · Conc = 50 mg/mL · For 250 mg → 5 mL
Clinical
3 toolsCreatinine Clearance (CrCl)
Cockcroft-Gault equation for estimated kidney function. Essential for renal dose adjustment. Supports µmol/L and mg/dL. Auto-converts lb→kg.
CrCl = [(140−age) × weight × F] ÷ (0.814 × SCr µmol/L)
F = 1.0 for males · F = 0.85 for femalesCKD Stages: ≥90 Normal · 60–89 Mild · 30–59 Moderate · 15–29 Severe · <15 Failure
Renal Dose Adjustment
Estimated dose or interval adjustment based on CrCl. Use with the CrCl calculator above. Supports dose reduction and interval extension methods.
CrCl ≥50: 100% · CrCl 30–49: 75% · CrCl 15–29: 50% · CrCl <15: 25%
Interval extension factors:
CrCl ≥50: ×1 · CrCl 30–49: ×1.5 · CrCl 15–29: ×2 · CrCl <15: ×3
Body Surface Area (BSA)
BSA in m² using Du Bois, Mosteller or Haycock formula. Used for chemotherapy dosing, cardiac index and paediatric calculations.
Mosteller: √(H × W ÷ 3600)
Du Bois: 0.007184 × H⁰·⁷²⁵ × W⁰·⁴²⁵
Haycock: 0.024265 × H⁰·³⁹⁶⁴ × W⁰·⁵³⁷⁸
Average adult BSA ≈ 1.7–1.8 m²Mosteller is recommended for most clinical use. Haycock is preferred for neonates and children.
Business
3 toolsPharmacy Markup & Margin
Calculate markup %, gross margin % or selling price from cost. Three modes — works from cost+sell, cost+markup or cost+margin.
Markup % = (Profit ÷ Cost) × 100
Margin % = (Profit ÷ Sell) × 100
Example: Cost $8.50, Sell $14.95 → Profit $6.45Markup = 75.9% · Margin = 43.1%
Margin is always lower than markup for the same product.
Dispensing Fee Estimator
Estimate total dispensing fee revenue for a period. Add average product cost and markup to get total revenue estimate.
Professional dispensing fee: ~$8.40 · Handling fee: ~$3.70 · Dangerous drug fee: ~$3.46
Fees are indexed annually — always confirm current rates with the PBS schedule.
Cost Per Day Calculator
Daily, weekly, monthly and annual cost of a medication from pack price, pack quantity, dose and frequency. Useful for patient counselling and medication reviews.
Daily units = Dose per admin × Doses per day
Days per pack = Pack qty ÷ Daily units
Cost per day = Pack price ÷ Days per pack
Example: $22.50 pack · 30 tablets · 1 tablet ODDays per pack = 30 · Cost per day = $0.75 · Per year = $273.75