Dilution Calculator
Diluting a stock solution follows C1V1 = C2V2. Enter any three of the two concentrations and two volumes, and it solves for the fourth on the spot.
The dilution rule is C1·V1 = C2·V2 — concentration times volume stays constant as you add solvent. Enter any three and leave the fourth blank. Keep the two concentrations in the same units and the two volumes in the same units, and the answer comes out in those.
C1
2
V1
25
C2
0.5
V2
100
Solving for V1 tells you how much stock solution to measure out. The rest of the final volume is just solvent — so V2 minus V1 is the water (or buffer) you add.
How it works
When you dilute a solution you add solvent, not solute — so the total amount of dissolved stuff doesn't change. That's what C1V1 = C2V2 captures: concentration times volume is constant before and after.
Enter three of the four values and leave the last one blank. The tool rearranges the equation for the missing piece — for example V1 = C2·V2 / C1 to find how much stock to pour out — and skips a divide-by-zero rather than showing a broken number.
Units just have to be consistent. Keep both concentrations in the same units (molarity, percent, whatever) and both volumes in the same units, and your answer comes back in those same units.
Frequently asked questions
How much stock solution do I need for a dilution?
Leave V1 blank and fill in the other three. The tool computes V1 = C2·V2 / C1 — the volume of concentrated stock to measure out. The rest of the final volume is solvent you add on top.
Do the concentrations need to be in molarity?
Any concentration unit works as long as both are the same. Percent, molarity, or mg/mL all give correct results, because the units cancel on each side of C1V1 = C2V2.
Why is my final concentration lower than the starting one?
That's dilution doing its job. Adding solvent increases the volume, so the same amount of solute is spread thinner and the concentration drops. C2 will always be at or below C1.