Formulas

• Concentration (mg/mL) = total drug in vial ÷ final solution volume.
• Volume to administer (mL) = ordered dose ÷ concentration.

Worked example

A 1 g (1000 mg) vial reconstituted to a final volume of 10 mL → 100 mg/mL. Ordered dose 250 mg → 250 ÷ 100 = 2.5 mL.

Notes

• Use the final volume from the label, not the diluent volume added – powder displacement makes them differ.
• Some labels state the resulting concentration directly; if so, use it.
• Check stability and storage time after reconstitution.

Educational use only – for checking and learning medication math. Always verify doses against the order, the drug reference and a pharmacist. Reviewed 2026-08-23.