What this calculator does
Serial dilution series works out final concentration after a series of equal-factor dilutions, and the concentration at each step. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Initial concentration (CFU/mL) | A number, measured in CFU/mL. Starts at 100000000. |
| Dilution factor per step | A number. Starts at 10. |
| Number of dilution steps | A number. Starts at 5. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with initial concentration
Every other input is held at the calculator’s starting values while initial concentration varies. Select any row to load that scenario into the calculator.
| Initial concentration (CFU/mL) | Final concentration | Total dilution factor | Log₁₀ total dilution |
|---|---|---|---|
| 50,000,000 | 500 CFU/mL | 100,000× | 5.000 |
| 75,000,000 | 750 CFU/mL | 100,000× | 5.000 |
| 100,000,000 | 1,000 CFU/mL | 100,000× | 5.000 |
| 150,000,000 | 1,500 CFU/mL | 100,000× | 5.000 |
| 200,000,000 | 2,000 CFU/mL | 100,000× | 5.000 |
| 300,000,000 | 3,000 CFU/mL | 100,000× | 5.000 |