C1V1 = C2V2 Dilution Calculator
Calculator
Enter the three known values, then choose what to solve for. Volume units (e.g., mL)
Educational use only. Always interpret results in clinical context and verify with local policies.
Written by George Lambroglou, RN • Formula checked against listed references • Last reviewed 21 Jun 2026
Solve the dilution equation for the missing concentration or volume. Enter the three known values and choose what you want to calculate.
How C1V1 = C2V2 Works
The C1V1=C2V2 equation represents conservation of solute: the amount of drug/solute before dilution equals the amount after dilution. When you add diluent, you increase the final volume (V2), so the final concentration (C2) decreases.
Key safety point: use final total volume (V2) — not the volume of diluent added. Diluent volume is calculated separately as V2 − V1.
Quick checks (avoid the classic errors):
- C1 and C2 must be the same concentration units (convert first if needed).
- V1 and V2 must be the same volume units.
- For a typical dilution, C2 should be lower than C1.
Formula
Worked Examples
Example 1: You have 10 mg/mL stock. You want 1 mg/mL in a final volume of 50 mL. What volume (V1) of stock do you need?
V1 = 50 ÷ 10 = 5 mL
Diluent = 50 − 5 = 45 mL
Example 2: You take 20 mL of 5 mg/mL solution. What concentration (C2) do you get if you make it up to 100 mL?
C2 = (5 × 20) ÷ 100 = 1 mg/mL
Test questions
Quick practice checks to reinforce setup and avoid the most common C1V1=C2V2 mistakes (education only).
1) In C1V1=C2V2, what does V2 represent?
2) True/False: C1 can be in mg/L while C2 is in mg/mL if you’re careful.
3) If C1=8 mg/mL, V1=10 mL, and V2=40 mL — what is C2?
4) If C1=20 mg/mL, C2=5 mg/mL, V2=60 mL — what is V1?
5) Using Q4, how much diluent is added?
6) Sanity check: for a typical dilution where C2 < C1, should V1 be smaller than V2?
7) If your calculator shows negative diluent, what’s the first thing you check?
8) Can dilution achieve a higher concentration target (C2 > C1) by adding diluent?
When This Is Used
- •Preparing diluted solutions from concentrated stock
- •Adjusting medication concentrations for paediatric dosing
- •Pharmacy compounding and aseptic preparation
- •Double-checking dilution and concentration arithmetic
Clinical safety note: Always confirm concentrations, units, and local protocols. Use independent double-checks for high-risk medications and small-volume dilutions.
Related Calculators
Frequently Asked Questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Further Reading
This calculator is based on established dilution and pharmaceutical standards from authoritative sources across healthcare disciplines.
International Standards
Australia Resources
United Kingdom Resources
United States Resources
Tip: If your answer looks wrong, it’s almost always a unit mismatch (e.g., mg/mL vs mg/L) or using diluent volume instead of final total volume (V2).