Molar Absorptivity Calculator
Enter absorbance, concentration, and path length to find molar absorptivity.
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How to use
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About this calculator
The Beer-Lambert law states A = ε·c·l, where A is absorbance, c is molar concentration, and l is the path length of light through the sample (typically a 1 cm cuvette). Solving for ε gives the molar absorptivity (also called the molar extinction coefficient), measured in L·mol⁻¹·cm⁻¹ — a constant specific to a given substance at a given wavelength.
Molar absorptivity values are used to identify compounds and calculate unknown concentrations from a measured absorbance reading in UV-Vis spectrophotometry. It's a routine calculation for analytical and biochemistry labs — for example, quantifying DNA or protein concentration from A260/A280 readings — and for pharmaceutical quality-control testing.
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