Beer-Lambert Law (Biology) Calculator
OD600 Bacterial Growth
Estimate bacterial cell density from OD600 optical density reading
Absorbance from Transmittance
Convert percent transmittance to absorbance
Formula
A = −log₁₀(T). Cell density ≈ OD600 × conversion factor (e.g., 8 × 10⁸ cells/mL for E. coli). Corrected OD = raw OD × dilution factor.
Frequently Asked Questions
What is OD600?
OD600 is the optical density of a cell culture measured at 600 nm wavelength. It estimates bacterial cell density. An OD600 of 1.0 corresponds to roughly 8 × 10⁸ cells/mL for E. coli, though this varies by species.
When is OD600 not linear?
OD600 readings above ~1.0 are typically outside the linear range of most spectrophotometers. At high densities, multiple scattering causes underestimation. Dilute the sample and re-measure for accuracy.
What is the relationship between absorbance and transmittance?
Absorbance A = −log₁₀(T) = −log₁₀(%T/100). An absorbance of 1 corresponds to 10% transmittance; absorbance of 2 corresponds to 1% transmittance.
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