Formula: Water Volume (mL) = Total Peptide (mg) ÷ [Target Dose (mg) ÷ Desired Injection Volume (mL)]. Example: To get 250mcg (0.25mg) in 0.1mL from a 10mg vial: 10 ÷ (0.25 ÷ 0.1) = 10 ÷ 2.5 = 4mL bacteriostatic water needed.
USP compounding math provides detailed calculation methodologies.