Reconstitution Calculator
Convert vial powder strength into a ready-to-use solution by calculating the final volume and diluent to add.
Volume occupied by the powder after reconstitution (manufacturer data).
Volume already in the vial, if any.
How to Use This Calculator
Check vial potency
Enter the total amount of drug powder available in the vial (mg).
Set target concentration
Provide the desired final concentration in mg/mL for dosing or storage.
Account for displacement
If the package insert lists a displacement volume, enter it to avoid over-dilution.
Read diluent volume
Add the calculated volume of diluent to the vial to reconstitute to the target strength.
Formula
V_final = mg_powder / (mg/mL target)
Diluent to add = V_final − displacement − existing_diluent
Reconstitution assumes complete dissolution of powder with displacement volume accounting for the powder’s contribution to final volume.
Example
500 mg vial targeting 100 mg/mL with 10 mL displacement: V_final = 5 mL; diluent = 5 − 10 = -5 mL → not feasible. Instead, targeting 50 mg/mL yields V_final = 10 mL, diluent = 0 mL beyond displacement.
Full Description
Reconstitution converts a dry powder medication into an injectable or oral liquid by adding diluent. Accurate volumes ensure dosing accuracy and stability.
This calculator uses drug amount, target concentration, and displacement volume to determine how much diluent to add and the final concentration achieved.
Frequently Asked Questions
What is displacement volume?
It is the volume occupied by the powder after dissolution, effectively reducing how much diluent is needed.
Can I ignore displacement?
For small volumes or when data is unavailable, displacement may be negligible. However, for concentrated products, use manufacturer data.
Does diluent temperature matter?
Use the diluent recommended by the manufacturer at the specified temperature to ensure solubility and stability.
How precise should measurements be?
Use syringes or graduated cylinders for accuracy. Small errors in volume can significantly impact final concentration.
Can I reconstitute partially?
Yes. Adjust the target concentration and calculate accordingly, but note the resulting vial concentration for dosing.