Beer-Lambert Law Calculator
Calculator
\[ A = \varepsilon \cdot c \cdot l \qquad A = -\log_{10}(T) \]
where A, ε, c, l, and T denote absorbance, molar absorptivity (L·mol⁻¹·cm⁻¹), concentration (mol/L), path length (cm), and transmittance.
Beer-Lambert Law — Solve For
Result
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Absorbance ↔ Transmittance Converter
About This Tool

The Beer-Lambert law — A = ε·c·l — quantifies the absorption of light by a solution. Absorbance A is dimensionless and equal to the negative base-10 logarithm of transmittance T. Molar absorptivity ε (also called the molar extinction coefficient) is a substance-specific constant in units of L·mol⁻¹·cm⁻¹, expressing how strongly a species absorbs at a given wavelength. Path length l is typically 1 cm for standard cuvettes. This calculator lets you solve for any one of the four variables, and also displays transmittance, percent transmittance, and percent absorption as supporting outputs. The absorbance–transmittance converter at the bottom is useful for working between different spectrophotometer output formats. The Beer-Lambert law underpins UV-Vis spectroscopy, colorimetry, and quantitative analysis of proteins, DNA, dyes, and metal complexes.