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Pharmaceutical Calculators

Dilution Calculator

Calculate stock solution volume and diluent needed using the C1V1=C2V2 conservation of mass formula. Used in pharma labs, HPLC prep, and buffer preparation.

Formula
C1 × V1 = C2 × V2
C1 = Stock concentration    V1 = Volume of stock needed (solved)
C2 = Target concentration    V2 = Total final volume desired
V1 = (C2 × V2) / C1
Enter Values
Stock Volume (V1)
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Diluent to Add
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Dilution Factor
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×
Verification
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How to Use

1
Enter your stock solution concentration (C1) and select its unit (mg/mL, μg/mL, etc.).
2
Enter your desired final concentration (C2) using the same unit as C1. The target must be lower than the stock concentration.
3
Enter the total final volume you need to prepare (V2) and choose your volume unit (mL, L, or μL).
4
Click Calculate — instantly see the volume of stock to take (V1), volume of diluent to add, dilution factor, and a concentration verification.

Worked Example

Example Calculation

You have a 100 mg/mL stock solution and need 10 mL of a 5 mg/mL solution:

V1 = (C2 × V2) / C1 = (5 × 10) / 100 = 0.5 mL of stock

Diluent = V2 − V1 = 10 − 0.5 = 9.5 mL of diluent

Dilution factor = C1/C2 = 100/5 = 20×

About the C1V1=C2V2 Formula

The dilution equation C1V1 = C2V2 is derived from the conservation of mass principle: the total amount of solute (in moles or mass) does not change when you add diluent to a solution. Since concentration = amount / volume, multiplying each side's concentration by its volume yields the total amount of solute, which must be equal before and after dilution.

This formula is universally applicable across pharmaceutical, clinical, and research settings — from preparing IV infusion solutions and HPLC mobile phases to diluting stock reagents for cell culture assays. The only requirement is that C1 and C2 are expressed in the same units.

For serial or step-wise dilutions (where a diluted solution is diluted again), use the Serial Dilution Calculator.

Frequently Asked Questions

C1V1=C2V2 is the dilution formula stating that initial concentration multiplied by initial volume equals final concentration multiplied by final volume. It is derived from the conservation of mass principle — the total amount of solute remains constant during dilution. Rearranged to V1 = (C2 × V2) / C1, it tells you exactly how much stock solution to take.
The dilution factor is the ratio of the final volume to the initial volume (V2/V1), equivalently expressed as C1/C2. For example, a 1:10 dilution has a dilution factor of 10×, meaning the final solution is 10 times less concentrated than the stock. It is used as a shorthand to describe how much a solution has been diluted.
This requires a 100× dilution factor. Take 1 part stock solution and add 99 parts diluent. For a 10 mL final volume: V1 = (10 × 10) / 1000 = 0.1 mL stock, then add 9.9 mL diluent. Enter C1=1000, C2=10, V2=10 mL in this calculator to confirm.
This calculator works with any concentration unit — mg/mL, μg/mL, mg/L, %, mol/L, or mmol/L — as long as C1 and C2 are expressed in the same unit. Volume inputs are converted to mL internally. The key requirement is unit consistency between the two concentration inputs.
The underlying mathematics — C1V1=C2V2 — is identical. However, in pharmaceutical settings, concentration accuracy is critical for patient safety, and sterility must be maintained throughout. Pharmaceutical dilutions are typically performed under GMP conditions using validated equipment, with documented calculations and sterile diluents.
Dilution reduces the concentration of a solute already in solution by adding more solvent. Dissolution is the process of dissolving a solid (or gas) into a solvent to create a solution from scratch. Adding water to a 100 mg/mL drug solution is dilution; dissolving a 100 mg tablet into 1 mL of water is dissolution.

Related Calculators

🧪 Serial Dilution Calculator ⚗️ Molarity Calculator 📏 Unit Converter 💉 IV Drip Rate Calculator