🔬 Molar Extinction Coefficient Calculator
Use the Beer-Lambert law to find a compound’s molar extinction coefficient (molar absorptivity) from a measured absorbance, sample concentration, and cuvette path length.
What the molar extinction coefficient tells you
The molar extinction coefficient (also called molar absorptivity, symbol ε) describes how strongly a chemical species absorbs light at a particular wavelength. A high value means a compound absorbs strongly even at low concentrations, which is why it is a key parameter in UV-Vis spectroscopy for identifying and quantifying substances.
The formula
This calculator rearranges the Beer-Lambert law, A = ε × c × l, to solve for ε = A ÷ (c × l), where A is the measured absorbance (unitless, in absorbance units), c is the molar concentration of the absorbing species in mol/L, and l is the path length of light through the sample in centimeters.
Note: The Beer-Lambert law assumes dilute, non-scattering, monochromatic light conditions; at very high concentrations the relationship can become non-linear. This tool is for general lab and educational reference, not a substitute for calibrated spectrophotometer analysis.