Dilution calculator (C₁V₁ = C₂V₂)
How much stock to take, and how much diluent to add to reach the volume you want.
Free, no account needed. Nothing you type is sent anywhere or stored — the arithmetic runs in your browser.
Inputs
Results
Stock to take
1mL
- Diluent to add
- 9mL
- Fold dilution
- 10
Why there are no units on the concentrations
In C₁V₁ = C₂V₂ the concentrations appear on both sides and cancel, so the arithmetic does not care whether you work in mg/mL, µM, percent or X — it only cares that both are in the same one. That is the usual way this goes wrong: a stock written in mg/mL against a target written in µg/mL is out by a thousand, and nothing about the number that comes back looks unusual.
The volume is in real units, because it is the thing you measure.
“Add” and “make up to” are not the same instruction
The diluent figure is the final volume minus the stock volume — what to add if you are combining the two. It assumes volumes are additive, which is close enough at ordinary dilutions and not true for concentrated solutions.
When it matters, take the stock and make it up to the final volume against a mark, rather than adding the calculated diluent to it. Same target, and the mark does not care whether the volumes added up.
If the stock volume comes out tiny
A dilution that asks for less than a microlitre or two is a dilution you cannot pipette accurately, and the error carries into everything made from it. Do it in two steps instead — an intermediate dilution you can measure, then the final one from that.