How do I calculate the dilution factor if I need to create a more dilute solution from a concentrated stock?

Use the formula: C1 × V1 = C2 × V2, where C1 is current concentration, V1 is volume to transfer, C2 is desired concentration, and V2 is final total volume. Example: To dilute 2mg/mL to 0.5mg/mL in 4mL total, transfer 1mL of stock and add 3mL bacteriostatic water (2mg/mL × 1mL = 0.5mg/mL × 4mL). USP dilution calculations provide detailed methodologies.