Serial Dilution Calculator
By Santaji GadepatilinUpdated October 27, 2026
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Type in any field to change it. Press × on a value to calculate that field instead.
How to use this calculator
Enter the starting concentration, the dilution factor per step and the number of steps. The total dilution and final concentration are calculated (any concentration unit works).
Formulas
Total dilution = fn C = C₀ ÷ fn
Example
10⁸ cells/mL diluted 1:10 six times:
- Total dilution = 10⁶
- Final concentration = 100 cells/mL
Plating 100 µL gives about 10 colonies — easy to count.
Frequently asked questions
What is a serial dilution?
A series of step-by-step dilutions, each by the same factor, to reach very low concentrations accurately.
How do I make a 1:10 dilution?
Mix 1 part sample with 9 parts diluent — for example 100 µL into 900 µL.
How do I count CFU from a plate?
CFU/mL = colonies ÷ (volume plated in mL × total dilution).