Free tool
Serial dilution calculator
How much stock, and how much diluent, to reach a target concentration at a given final volume. The equation is C₁V₁ = C₂V₂ — the arithmetic below is that, rearranged.
What you have, and what you want
Start from a common job below, or type your own numbers.
Your answer
Measure the stock first, then bring it up to the final volume.
Show the other figures
- Same volume in microlitres
- — µL
- Diluent to add
- — mL
- Dilution factor
- — ×
Arithmetic only. This tool converts between mass, volume and concentration for laboratory preparation and dilution planning. It is not dosing guidance, and nothing here is a therapeutic claim. All materials are supplied for in-vitro laboratory research use only.
How the arithmetic works
V₁ = (C₂ × V₂) ÷ C₁
The most common error here is not the equation, it is the word final. The diluent figure is what you add to the stock to reach the final volume — not the final volume itself. Adding 10 mL of diluent to 0.5 mL of stock gives 10.5 mL and a concentration five percent off target. Bring the stock up to volume; do not add volume to it.
For large dilution factors, work in steps. Measuring 0.01 mL accurately is difficult; two sequential ten-fold dilutions are far more reproducible than one hundred-fold, because each step uses a volume your pipette handles well.
Frequently asked
What is the C1V1 = C2V2 formula?
It states that the amount of solute is unchanged by dilution: concentration times volume before equals concentration times volume after. Rearranged for the volume of stock you need, it becomes V₁ = (C₂ × V₂) ÷ C₁.
How much diluent do I add?
Final volume minus stock volume. If you need 1 mL of stock to make 10 mL, you add 9 mL of diluent — not 10.
Why dilute in steps instead of all at once?
Accuracy. A single hundred-fold dilution may require measuring 0.01 mL, which is at the edge of most pipettes. Two ten-fold steps each use a comfortable volume, and the error compounds far less.