Dilution calculator
Work out how much stock and diluent to combine for a target concentration.
Stock volume to take
Add 9.5 mL of diluent. That is a 1 in 20 dilution.
V₁ = C₂V₂ ÷ C₁- Conservation of amount of substance on dilution — IUPAC Compendium of Chemical Terminology (the Gold Book), 2019
When to use this
Use this whenever you have a stock and need a working solution: it solves C₁V₁ = C₂V₂ for whichever of the four terms you are missing. It works in molar or mass-per-volume units, as long as both concentrations are the same kind. If you instead need to keep a recipe’s proportions while changing the batch size, the recipe scaler is the right tool.
Worked example
You have a 1 M stock and need 10 mL at 50 mM.
- Solve for
- Stock volume
- Stock concentration
- 1 M
- Final concentration
- 50 mM
- Final volume
- 10 mL
Result
Add 9.5 mL of diluent to it — a 1 in 20 dilution.
What people get wrong
- Adding the final volume of diluent to the stock rather than making up to the final volume. The number the tool gives for diluent is already the difference.
- Mixing unit kinds. Molar and mass-per-volume cannot be compared without a molar mass, which is why they are a toggle rather than one list.
- Pipetting under about 5 µL for a single step. Below that the instrument error is a real fraction of the dose; make an intermediate dilution instead.
Questions
+Does "1:10" mean one part in ten, or one part in eleven?
Both are used in the wild, which is why this tool asks for concentrations and volumes rather than a ratio. Write down which convention you meant.
+Can I dilute in mg/mL?
Yes — switch the concentration kind to mass per volume. C₁V₁ = C₂V₂ holds in any unit as long as both sides share it.
+What if I need a very large dilution?
Do it in steps. A 1 in 10,000 dilution in one move means 1 µL into 10 mL, where a single bubble ruins it; four tenfold steps use volumes you can see.
Related tools
- Serial dilution calculator — Plan a dilution series and get the transfer volume for every step.
- Molarity calculator — Convert between mass, molar concentration and volume for a solution.
- Molecular weight calculator — Compute molar mass from a chemical formula, including hydrates.
Science last reviewed .