Stock + Volume to Achieved Concentration
Calculate the final concentration achieved when adding a measured volume of stock solution to a measured volume of diluent.
Educational use only. Always verify against local policy and product information.
How it works
When you add a volume (V1) of a stock solution with a known concentration (Cstock) to a volume (V2) of diluent, the total amount of drug stays the same but is now distributed through a larger total volume.
This calculator uses mass balance: amount of drug added = Cstock × V1, then divide by total volume (V1 + V2) to get the achieved concentration.
Formula
Worked examples
Example 1: Simple dilution
You have 10 mg/mL morphine. You take 2 mL stock and add 18 mL diluent. What is Cfinal?
Example 2: Paediatric dilution
Furosemide 40 mg/mL: draw 1 mL and dilute with 9 mL. What is Cfinal?
Example 3: Reconstitution
A vial contains 500 mg powder. Reconstitute to 10 mL. What is concentration?
When this calculator is used
- •Preparing a diluted concentration from a stock solution and known volumes
- •Reconstituting a vial and diluting the result further
- •Creating paediatric or neonatal preparations from standard concentrations
- •Teaching dilution and concentration fundamentals
- •Quick verification as a second-check step
Clinical safety reminder: Always verify dilution calculations independently and confirm the final concentration matches the prescription and local protocol.
Related calculators
Frequently asked questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & sources
Institute for Safe Medication Practices (ISMP)
Medication safety guidance and error prevention
WHO Medication Safety
Global medication safety initiatives and guidance
ACSQHC Medication Safety Standard (NSQHS)
Australian medication safety standard
Clinical disclaimer: Educational use only. Follow local policy and product information.