Calculate absorbance from molar absorptivity, concentration, and optical path length.
| Absorbance A | – |
Use this calculator in a UV-Vis lab when you have ε from a paper or a standard-curve slope, a cuvette path, and a concentration, and you want A before you measure.
The calculation is A = ε × c × l. Keep ε, c, and l in matching units, typically L·mol⁻¹·cm⁻¹, mol/L, and cm. Path length can be entered in centimetres (cm) or inches (in); the calculator converts to centimetres. Absorbance is dimensionless.
This is the linear Beer–Lambert law. It does not correct for stray light, fluorescence, or deviations at high absorbance.
ε: Molar absorptivity, usually L·mol⁻¹·cm⁻¹ from the method or a paper.
c: Concentration in mol/L if ε is in L·mol⁻¹·cm⁻¹.
Path length: Optical path in cm or in. A standard cuvette is 1 cm.
Absorbance A: Predicted absorbance (A = εcl).
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