How to use
- Enter three of the four values — C1 (initial concentration), V1 (initial volume), C2 (final concentration) and V2 (final volume). Leave the one you want blank.
- Each value carries its own unit. C1 in mM and C2 in μM is fine; the conversion happens internally.
- The result card shows the calculated value, with the dilution factor (C1 ÷ C2) underneath it.
- copies/μL cannot be mixed with molar units. Switching one concentration to copies/μL switches the other one too.
Exponents can be entered with e — for example, 1.5×10⁻⁵ is entered as 1.5e-5.
Formula & notes
C1V1 = C2V2 is one fact written as an equation: diluting a solution does not change how much solute is in it. Concentration × volume is the amount of solute, so that product has to match before and after. Adding solvent does not create or destroy the dissolved substance.
Knowing three of the four values, the fourth comes from rearranging the equation.
- Initial concentration
- C1 = C2 × V2 ÷ V1
- Initial volume
- V1 = C2 × V2 ÷ C1
- Final concentration
- C2 = C1 × V1 ÷ V2
- Final volume
- V2 = C1 × V1 ÷ C2
The dilution factor is C1 ÷ C2, which is the same as V2 ÷ V1. A tenfold dilution takes the concentration to a tenth and the volume to ten times. It is not one of the four values above but a separate result, which is why the card shows it on its own line.
Practical notes
- V2 is the final volume, not the amount of solvent you add. The diluent to add is V2 − V1. This is where the mistake is made most often. If you want the preparation figures directly, use the reagent preparation calculator.
- When V1 works out very small — below about 1 μL — the pipetting error becomes a large fraction of it. An intermediate dilution is more accurate.
- Volumes do not always add. Concentrated solutions and alcohols contract on mixing, so it is better to make the final volume up in a volumetric flask.
- Units may differ from field to field and are converted internally, but write the unit down along with the value when you copy the result.
- The calculation assumes a homogeneous solution. Precipitation or adsorption onto the vessel wall will put the real concentration somewhere else.