Spectrophotometric Cell Count Calculator

Summary

Convert OD600 absorbance readings to estimated bacterial cell count (cells/mL) using Beer-Lambert law or a custom conversion factor.

How it works

1. Enter the measured OD600 absorbance value from your spectrophotometer.
2. Select a preset organism (E. coli, S. cerevisiae, etc.) or enter a custom cells-per-OD conversion factor.
3. Input the sample dilution factor if the culture was diluted before reading.
4. Optionally adjust the cuvette path length if it differs from the standard 1 cm.
5. The calculator applies Beer-Lambert law and outputs estimated cells/mL and total cells.
6. Results update instantly; use the copy button to capture values for your lab notebook.

Use cases

• Estimate E. coli culture density before induction in protein expression experiments.
• Standardize inoculum density for antimicrobial susceptibility testing.
• Monitor yeast growth curves during fermentation without cell counting.
• Calculate CFU/mL equivalents for sample preparation in flow cytometry.
• Determine when to harvest cells at mid-log phase for downstream assays.
• Validate dilution series before plating for colony counting.
• Quick sanity check on culture density before DNA or RNA extraction.
• Teaching aid for microbiology lab courses demonstrating Beer-Lambert law.

Frequently Asked Questions