Dilution Calculator
Calculate the volume of stock solution required to prepare a diluted solution of a specific concentration and volume. Uses the fundamental dilution equation C1V1 = C2V2, where V1 is the unknown stock volume to add.
Calculator
Enter values and calculate to see the result
Stock solution needed (V1)
Bench note
C1V1 = C2V2 → V1 = (C2 × V2) / C1
The dilution equation states that the amount of solute is conserved. Multiply the desired final concentration (C2) by the final volume (V2), then divide by the stock concentration (C1) to find the stock volume (V1) to add. The remainder is diluent: V2 − V1.
About this calculation
What this is
Dilution rests on the conservation of solute: C1·V1 = C2·V2. Whatever the concentration of the stock, the amount of solute in the final mix is set by the final concentration and final volume — so the stock volume to add is V1 = C2·V2 / C1.
Why it is used
Almost every working solution in the lab starts from a more concentrated stock. Knowing how much stock to add avoids waste, prevents under- or over-dilution, and makes protocols reproducible.
Why this calculator exists
C1V1 = C2V2 is short, but the unit prefixes (M, mM, µM, %, ×) and the order-of-magnitude jump from stock to working concentration make the arithmetic error-prone. The calculator handles the unit reconciliation and reports the stock volume directly.
Key assumptions
- The stock and final concentrations are expressed with units the calculator can reconcile (M-class, mass/volume, %, or fold).
- The final volume is the volume of the diluted solution, not the volume of diluent added.
- Mixing is additive in the dilute regime — true for most bench dilutions, not for solvent swaps.
Limitations
- It does not account for viscosity differences between stock and diluent.
- For very high dilutions (>1:10000) small pipetting errors dominate; use serial dilution.
- It does not adjust for temperature or for solutes that change volume on dissolution.
What this calculates
- Stock volume (V1)
- Volume of stock solution to add to the diluent.
- Diluent volume
- Volume of diluent (e.g. water, buffer) to add.
- Dilution factor
- Ratio of stock concentration to final concentration (C1/C2).
Frequently asked questions
How do I use the dilution calculator?
Enter your stock concentration (C1) and its unit, the desired final concentration (C2) and its unit, and the final volume (V2) you want to prepare. The calculator returns the stock volume to pipette (V1), the diluent volume to add, and the dilution factor. For example, to make 100 mL of 1 mM from a 10 mM stock, enter C1 = 10 mM, C2 = 1 mM, V2 = 100 mL and get V1 = 10 mL plus 90 mL diluent.
What formula does the dilution calculator use?
It uses the dilution equation C1V1 = C2V2, rearranged to solve for the stock volume: V1 = (C2 x V2) / C1. The diluent volume is then V2 minus V1, and the dilution factor is reported as C1 divided by C2. The equation holds because adding solvent dilutes the sample but leaves the amount of solute unchanged.
How do I calculate a dilution factor?
The dilution factor is the stock concentration divided by the final concentration (C1/C2), and the calculator reports it alongside the volumes. A factor of 10 means the working solution is ten times more dilute than the stock, so you take 1 part stock and make the total volume up to 10 parts. Do not confuse the factor with the 1:9 mixing ratio of stock to diluent — the factor counts the final total volume.
Which units does the dilution calculator support?
Concentrations can be entered in M, mM, µM, nM, mg/mL, µg/mL, ng/mL, percent (v/v or w/v), or fold (x); volumes in L, mL, or µL. Enter C1 and C2 in the same unit — the calculator does not convert between concentration units, and percent and fold values are treated as consistent ratios that are not interconverted. A prefix mismatch (mM vs µM) changes the answer a thousand-fold, so check both unit fields before reading the result.
Why does the dilution calculator reject my values or warn about the stock volume?
The tool errors when C2 is not smaller than C1, because diluting means lowering the concentration, not raising it. It also warns when the calculated stock volume falls below the 2 µL practical pipetting floor, since air-displacement pipettes lose accuracy there — prepare an intermediate dilution or reduce the final volume instead. Remember that V2 is the final solution volume, not the volume of diluent to add.
For research and educational use only. Not for clinical or diagnostic decisions. Always verify calculations independently before use in critical applications.