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Dilution Calculator

Dilute a concentrated stock solution to a target concentration using the classic C1V1 = C2V2 relationship. Enter your stock strength, the concentration you want and the final volume, and the calculator tells you how much stock to measure out and how much solvent to add.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

How to use this calculator

  1. Enter the stock concentration C1 and the desired concentration C2 in the SAME unit (for example both in mol/L or both in %).
  2. Enter the desired final volume V2 in millilitres.
  3. Read off the stock volume to use (V1), the solvent to add, and the overall dilution factor.

How it works

The number of moles (or mass) of solute is unchanged by dilution, so concentration times volume is conserved: C1 x V1 = C2 x V2. Rearranging for the unknown stock volume gives V1 = C2 x V2 / C1. The solvent you must add is simply the final volume minus that stock volume, V2 - V1, and the dilution factor is C1 / C2.

Worked example

Worked example. You have a 10 mol/L stock and want 500 mL of a 2 mol/L solution. V1 = 2 x 500 / 10 = 100 mL of stock. Solvent to add = 500 - 100 = 400 mL. The dilution factor is 10 / 2 = 5x, i.e. a 1-in-5 dilution.

Common mistakes

  • Mixing units — C1 and C2 must be expressed in the same unit, otherwise the ratio is meaningless.
  • Asking for a target concentration higher than the stock; you cannot concentrate a solution by adding solvent.
  • Adding the full final volume of solvent to the stock instead of only V2 - V1; always top up TO the final volume, don't add it on top.

Frequently asked questions

Do I add the solvent to the stock or the stock to the solvent?

Best practice is to measure the stock volume V1 into your vessel, then top up with solvent to the final volume V2. For concentrated acids the rule is 'add acid to water', so add the stock slowly to most of the solvent, then top up to volume.

What is a dilution factor?

The dilution factor is how many times more dilute the final solution is than the stock, equal to C1 / C2. A factor of 5x (or 1:5) means one part stock is made up to five parts total volume.

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