Dilution Calculator
Solve C1V1 = C2V2 for the stock volume, final volume or either concentration, in M, mM, µM, %, mg/mL or ×, and plan a serial dilution step by step.
Result…
How it's calculated
C1 × V1 = C2 × V2 V1 = C2 × V2 ÷ C1 V2 = C1 × V1 ÷ C2 Dilution factor = C1 ÷ C2 = V2 ÷ V1; diluent = V2 − V1 Serial: Cₙ = C0 ÷ Fⁿ; diluent per tube = transfer × (F − 1)
A dilution keeps the amount of solute the same and spreads it through more liquid, so concentration times volume is the same before and after: C1V1 = C2V2. Give any three of the four and the calculator finds the fourth, converting units first so the stock can be in mM and the final in µM, or the stock in mL and the final in µL. Molar units (M, mM, µM, nM) convert among themselves, as do mass units (% w/v, mg/mL, µg/mL); turning one kind into the other needs the molar mass, which is a molarity calculation. A serial dilution repeats the same factor: moving one part into F − 1 parts of diluent divides the concentration by F each time, so n steps dilute by Fⁿ.
Your numbers, step by step
About the Dilution calculator
This dilution calculator solves C1V1 = C2V2 for whichever value you are missing: the volume of stock to take, the final volume, the final concentration or the stock concentration. Each value has its own unit, so the stock can be in mM and the target in µM, or the stock volume in µL and the final volume in mL. It converts them before solving. Concentrations can be M, mM, µM, nM, % w/v, mg/mL, µg/mL or a fold (×) stock such as a 10× buffer. Alongside the answer it shows the dilution factor and how much diluent to add. A second mode plans a serial dilution: the factor per step, the number of steps, the diluent each tube needs and the concentration after every step. Lab staff and students use it for buffers, standards and cell or bacterial dilution series. Every step of the working is shown.
How to use it
- Pick “One step (C1V1 = C2V2)” or “Serial dilution”.
- For one step, choose what to “Solve for”, then enter the other three values with their units.
- Read the answer, the “Dilution factor” and the “Diluent to add”.
- For a series, enter the “Starting concentration”, the “Dilution factor per step”, the “Number of steps” and the “Volume moved to each next tube”.
- Follow the steps list for the concentration in each tube.
Worked example
To make 20 mL of 250 µM from a 10 mM stock: V1 = 250 µM × 20 mL ÷ 10 mM = 500 µL of stock, a 40-fold dilution, topped up with 19.5 mL of diluent. For a tenfold series from 1 mg/mL over 4 steps, moving 100 µL into 900 µL each time, the tubes hold 0.1, 0.01, 0.001 and 0.0001 mg/mL, a total dilution of 10,000.
Updated
Questions people ask
How do I use C1V1 = C2V2?
Put the three values you know into the equation and solve for the fourth. To find the stock volume, V1 = C2 × V2 ÷ C1. C1 and C2 must be in the same kind of unit, and V1 and V2 in the same volume unit, or converted first.
What is a dilution factor?
It is how many times weaker the final solution is: C1 ÷ C2, which equals V2 ÷ V1. Taking 1 mL of stock into a final 10 mL is a dilution factor of 10.
Does a 1:10 dilution mean 1 part plus 10 parts?
Usage differs between labs. Here 1:10 means 1 part of stock in 10 parts of final volume, so 1 part stock and 9 parts diluent. Check which convention a protocol uses before you follow it.
How do I make a serial dilution?
Move a fixed volume from each tube into a tube of diluent that holds that volume × (factor − 1), mix, and repeat. After n steps the concentration is the start ÷ factorⁿ.
Can I dilute from molar units to mg/mL?
Not without the molar mass, because they measure different things. Convert first with the molarity calculator, then dilute.
Why doesn't my final volume come out exactly right?
Some liquids shrink or swell when mixed, so volumes don't always add up. Ethanol and water do this. When accuracy matters, make the solution up to the final volume in a volumetric flask rather than adding a measured volume of diluent.