Plan a dilution series in seconds: the concentration in every tube and exactly how much to transfer and how much diluent to add at each step.
Enter your stock, the fold-dilution per step and the transfer volume; the full series updates as you type.
Dilution series
Enter stock, factor, steps and transfer volume to see the series.
A serial dilution reaches a very low concentration through repeated small dilutions instead of one huge one. Each step dilutes the previous tube by the same factor, so concentrations fall geometrically: after n steps of a 10-fold series, the concentration is the stock divided by 10ⁿ. That is how standard curves, MIC assays and plate counts cover several orders of magnitude with ordinary pipettes.
For a dilution factor DF and a transfer volume V, every tube holds V × (DF − 1) of diluent. Adding the transferred V brings the tube to V × DF total, of which V is carried on to the next tube. Diluting 10-fold with a 100 µL transfer therefore means 900 µL of diluent per tube.
Starting from a 1000 ng/µL stock with a 10-fold factor, a 100 µL transfer and 4 steps: each tube gets 900 µL of diluent, and the series reads 100, 10, 1 and 0.1 ng/µL. The calculator prints exactly this table for your numbers.
Mix each tube thoroughly before transferring — pipetting errors compound through the series, which is why long series drift. Change tips between steps when carryover matters, and prepare a little more diluent than calculated to cover pipetting losses.
Each step divides the previous concentration by the dilution factor: after n steps the concentration is C₀ ÷ DFⁿ. The diluent per tube is the transfer volume times (DF − 1), so that adding the transfer brings every tube to the same total volume. The table is computed directly from these two formulas, with no rounding until display.
The results are unit-agnostic: concentrations come back in the unit you entered the stock in, and volumes in the unit of the transfer volume. The calculator is tested against the worked example on this page before every release.
This calculator is for general laboratory reference. Verify critical assays against your protocol and a qualified professional.
Short answers to the questions people ask most about serial dilutions.