How to use
- Enter the stock concentration, the target concentration and the target volume.
- The result card shows the volume of stock to transfer, with the volume of solvent to add underneath it.
- A single line below that states the preparation as an instruction you can follow directly.
- Concentration and volume each have their own unit.
💡 Exponents can be entered with e — for example, 1.5×10⁻⁵ is entered as 1.5e-5.
Formula & notes
This calculator uses the same equation as the dilution calculator, C1V1 = C2V2, but presents the answer from the bench's point of view. Where the dilution calculator fills in a blank, this one tells you what to mix and how much of it.
- Stock to transfer
- V1 = C2 × V2 ÷ C1
- Solvent to add
- V_solvent = V2 − V1
V2 here is the final volume you are making. Add V2 − V1 of solvent to V1 of stock and the whole comes to V2 at concentration C2.
Practical notes
- The solvent figure is what you add, not what you end up with. Swapping the two puts the concentration out, which is why the result card keeps them apart.
- For solutions whose volumes do not add — concentrated solutions, alcohols — it is more accurate to make up to the final volume in a volumetric flask than to add the calculated amount of solvent.
- When the stock volume works out very small, below about 1 μL, pipetting error dominates. Add an intermediate dilution, or make a larger batch.
- Viscous solutions cling to the pipette wall. Use reverse pipetting, or rinse the tip into the vessel.
- If the stock is less concentrated than the target, dilution cannot get you there and the calculation does not hold.
FAQs
The equation is the same; the presentation is not. The dilution calculator fills in whichever of C1, V1, C2 and V2 you left blank, while this one turns the answer into “this much stock plus this much solvent”. At the bench, the second is easier to work from.
For most dilute aqueous solutions, yes. Where volumes contract on mixing — concentrated solutions, alcohols — it is more accurate to add slightly less and bring the total up to the mark of a volumetric flask.
Dilution cannot produce it, so the calculation does not hold. You need a more concentrated stock, or to start again from the solid — in which case use the molarity calculator.
Two ways round it. Increasing the volume you are making — 10 mL to 100 mL, say — increases the transfer in proportion. Or dilute the stock once to an intermediate concentration and work from that.
Use the serial dilution prep calculator. It lays out the concentration at each step along with what to transfer and what to add.
That depends on the reagent. This calculator works out volumes and says nothing about stability. Follow the reagent's datasheet or your laboratory's procedure.
Often used together
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