UFC/mL a partir de diluição
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
This calculator converts the number of colony‑forming units (CFU) observed in a sample volume into a CFU per milliliter concentration. The user inputs the colonies counted, the dilution factor applied to the sample, and the final inoculated volume in milliliters. The tool applies the formula CFU/mL = colonies × dilution factor / volume.
The calculation works because each colony represents a cell or cell cluster that multiplied from a single bacterium or fungus. Multiplying the colony count by the dilution factor adjusts for the units present in the original sample. Dividing by volume normalizes the density, yielding the exact concentration per milliliter.
Use this calculator when quantifying microorganisms in water, food, cosmetics, or pharmaceutical products. It is valuable for quality control, academic research, and food safety testing. Accuracy relies on correct counts, well‑controlled dilutions, and precise volumes.
Be careful with counts exceeding 30 colonies, as precision decreases. Verify that the dilution factor is correct and that volume is measured accurately. Remember to clean and calibrate pipetting equipment to avoid erroneous counts.
Frequently asked questions
What does CFU/mL mean?
CFU/mL represents the number of colony‑forming units present in one milliliter of the original sample.
How do I determine the dilution factor?
The dilution factor is 1 divided by the dilution ratio; for example, 1:10 equals 10.
What is the ideal colony count?
For reliable results, the count should be between 30 and 300 colonies per plate.
Can I use the calculator with volumes smaller than 1 mL?
Yes, simply enter the exact volume in milliliters; the formula works for any measured volume.
How can I avoid counting errors?
Use proper Petri dishes, spread the sample evenly, and perform triplicate counts when possible.