Dilution Calculator (C1V1 = C2V2)
Enter three of the four values and the calculator works out the fourth, with clear mixing instructions.
Calculated on your device
Mix 200 mL of stock solution with 0.8 L of water or other diluent to make 1 L at 2%.
Dilution factor: 5 (stock : diluent = 1 : 4)
Results are a guide. Check them against your procedures and product labels before you rely on them.
How to use the dilution calculator
- 1Choose what you want to find. Most often, it's how much stock solution to use (V1).
- 2Enter the other three values and choose their units. Both concentrations must be the same kind of unit, such as both % or ppm, or both molar.
- 3Read the result. It tells you how much stock to measure and how much water or other diluent to add.
How the dilution formula works
When you dilute a solution, the amount of dissolved substance stays the same; only the volume grows. So concentration times volume is the same before and after, C1 × V1 = C2 × V2. C1 and V1 are the stock's concentration and the volume of stock you use. C2 and V2 are the concentration and total volume you end up with.
For example, to make 1 liter of a 2% solution from a 10% stock: V1 = 2% × 1 L ÷ 10% = 0.2 L. Measure 200 mL of stock and add 800 mL of water.
The dilution factor, C1 ÷ C2, says how many times weaker the diluted solution is. Lab protocols often write a factor of 10 as "1:10", meaning 1 part stock in 10 parts in total. That's 1 part stock to 9 parts water, so the calculator shows the stock-to-diluent ratio too.
For the most accurate result, add the stock to some of the water and then top up to the final volume in a measuring flask or cylinder. Liquid volumes don't always add up exactly when they're mixed.
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Frequently asked questions
What does C1V1 = C2V2 mean?
It's the dilution equation. C1 and V1 are the concentration and volume of the stock solution; C2 and V2 are the concentration and volume of the diluted solution. Diluting doesn't change the amount of dissolved substance, so both sides are equal.
Can I use different units for the two concentrations?
Yes, as long as they're the same kind. You can mix % and ppm (both mass per volume), or M and mM (both molar), and the calculator converts between them. Converting % to molar needs the substance's molar mass, so that isn't possible here.
How do I dilute a 10× buffer to 1×?
Choose × as the unit for both concentrations and enter C1 = 10 and C2 = 1. For 500 mL of 1× buffer, use 50 mL of the 10× stock and 450 mL of water.
Why can't the final concentration be higher than the stock?
Diluting only adds water or another solvent, so it always makes a solution weaker. To make it stronger, you would have to add more of the substance or evaporate some liquid.
Is what I type sent anywhere?
No. The calculation happens in your web browser, on your own device. Nothing you enter is sent to us or anyone else.
Is it free?
Yes. There is no sign-up and no limit on how often you use it.
Does it work on my phone?
Yes. It works in any modern browser on Android, iPhone, iPad, Windows, Mac and Linux.
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