Microbiology · PharmaWallah
Colony Counter & CFU Calculator
Count colonies. Verify your plate. Calculate CFU.
Count colonies from a plate photo
Automatically detect colonies from an agar plate image, review the count, and calculate CFU/mL.
Supported: JPG, JPEG, PNG, WEBP · Maximum file size: 10 MB
Works offline. Your image stays on your device.
CFU Calculation
Analyze a plate above, or enter a count you made by hand.
CFU/mL
Enter the colony count, dilution and volume plated.
Automated image-based colony counting, done on your device with classical computer vision (OpenCV). Always verify detected colonies manually.
CFU/mL = number of colonies ÷ (dilution fraction × volume plated in mL)
The dilution is written as a fraction: 10⁻⁴ is 0.0001. Example: 89 colonies from 0.1 mL of the 10⁻⁴ dilution → 89 ÷ (0.0001 × 0.1) = 8,900,000 = 8.9 × 10⁶ CFU/mL. This is the same as colonies × dilution factor ÷ volume, with a dilution factor of 10 000.
Colonies are found with classical image processing: plate detection (Hough circle), background correction, thresholding (Otsu or adaptive), morphological clean-up, and distance transform + watershed to separate touching colonies. No AI service is used and the image is not uploaded.
Common questions
No. The image is analysed inside this page on your device, and the tool works without an internet connection in the PharmaWallah app.
Treat it as a starting point. Zoom in, remove markers on bubbles, dust or lid reflections, and add colonies that were missed. The CFU calculation uses only the final verified count.
Touching colonies are separated when the shape clearly shows two lobes. When it does not, the region is left as one — remove it and add the colonies individually with Add colony.
Pick Dark or Light Colonies to match your plate, adjust Detection Sensitivity, and use Advanced Detection Settings for the colony size limits. If the dish itself was not found, select the plate manually.
Enter the count in CFU Calculation without analysing an image.
A commonly used practical counting range is around 30–300 colonies, but the appropriate range depends on the laboratory method and protocol.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy