Diluting a solution changes its volume, not the amount of solute in it. This solves the dilution equation for whichever value you need.
How it works
Dilution equation
M₁V₁ = M₂V₂
M₁, V₁ are the stock (starting) concentration and volume; M₂, V₂ are the final, diluted values.
Why dilution can never increase concentration
This is a conservation law, not a coincidence: the moles of solute (M×V) stays fixed while you add solvent, so as V rises, M must fall to keep the product constant. There’s no way to dilute a solution and end up more concentrated — that would require solute appearing from nowhere.
How to use this calculator
- Enter the stock concentration.
- Choose what you want solved — final concentration, stock volume needed, or final volume.
- Enter the remaining known values.
Frequently asked questions
Does it matter what volume units I use?
Just be consistent — mL and mL, or L and L, for both volumes. The ratio is what matters, so as long as both volumes use the same unit, the concentration units carry through correctly.
Can I use this for a serial dilution?
Yes, one step at a time — the output of one dilution step becomes the stock concentration for the next, since each step is an independent application of the same equation.
Why is this equation so widely used in a lab setting?
Because it’s the standard way to prepare a working solution of known concentration from a more concentrated stock, without needing to weigh out solid solute fresh every time — one stock solution can be diluted to many different working concentrations as needed.
What if I want to know how much solvent to add, not the final volume?
Subtract the stock volume from the final volume — the difference is the amount of solvent added to reach that final volume.
Is this the same equation as the one used for gas dilution?
The same underlying idea (concentration times volume is conserved) applies, though gas dilution problems are often phrased in terms of partial pressures rather than molarity — the structure of the equation is analogous either way.
