Plasmid MapPlan a serial dilution, one tube at a time
In a serial dilution, each new solution is prepared from the preceding dilution. With a constant per-step dilution factor F, the concentration in tube n is Cₙ = C₀ / Fⁿ. A tenfold step combines one part sample with nine parts diluent, giving ten parts mixed solution. It does not mean one part sample plus ten parts diluent.
Enter the starting stock concentration, per-step factor, number of diluted tubes and mixed volume per tube. The original stock is not counted as a tube. The calculator supports 1–24 steps and displays the sample source, transfer volume, diluent volume, concentration and retained volume for each one. It assumes the same dilution factor and mixed volume throughout the series.
Worked example: six tenfold steps
Start with 100 µM stock, choose a factor of 10, six diluted tubes and a mixed volume of 1 mL per tube. Each step transfers 100 µL of the preceding solution into 900 µL of diluent. The tube concentrations are 10, 1, 0.1, 0.01, 0.001 and 0.0001 µM. The final tube has a one-million-fold dilution relative to the original stock.
Only the first tube takes an aliquot from the original stock, so this plan needs 100 µL of original stock. Across all six tubes it uses 5.4 mL of diluent. Each onward transfer comes from a freshly mixed preceding tube, not from the original stock again.
Mixed volume is not retained volume
After mixing, each tube in the example contains 1 mL. Transferring 100 µL onward leaves 900 µL in tubes 1–5. Tube 6 keeps its full 1 mL because it supplies no further tube. Removing a well-mixed aliquot changes the amount remaining, not its concentration.
If you need equal retained volumes, choose Discard one transfer to equalize volumes. The plan then explicitly removes 100 µL from the last tube too, leaving 900 µL in all six. That option does not change concentrations or add a seventh dilution. It is a planning choice, not an instruction to discard material from an existing experiment.
Assumptions and practical limits
The calculation assumes complete mixing, additive volumes, no solute loss and no chemical reaction. It does not estimate pipetting uncertainty or evaporation. Small transfers may be difficult to measure with your equipment; the tool flags a calculated transfer below 1 µL. You can increase the mixed volume while retaining the same factor and concentrations.
The concentration unit stays consistent throughout the table. Choose a molar or mass-per-volume unit that describes your stock. For one stock-to-target calculation, use the single-step dilution calculator. To prepare that stock from a solid, use the molarity calculator and the correct compound formula or molar mass.
Serial dilution is illustrated in OpenStax Microbiology's discussion of microbial growth. This page applies the volume and concentration arithmetic only; it does not infer cell counts or select culture conditions. Save calculation records the inputs and assumptions. Table CSV contains the displayed tube plan, including units and retained volumes.