Beer-Lambert law calculator (A = ε × l × c)

This relation links the absorbance of a solution to its concentration, for a given path length and molar extinction coefficient.

A

· absorbance of the solution, dimensionless.

ε

· molar extinction coefficient of the solute, in L·mol⁻¹·cm⁻¹.

l

· path length travelled by the light (width of the cuvette).

c

· molar concentration of the solution.

The Beer-Lambert law assumes a homogeneous solution, monochromatic light. And no instrumental saturation; it stays linear only over a limited absorbance range (beyond it, the relationship between A and c departs from theory). The standard ε coefficient is defined for a path length in centimetres, check this convention before using it with another unit.

With ε = 10,000 L·mol⁻¹·cm⁻¹, a path length of 1 cm and a concentration of 10 µmol/L, the absorbance equals 0.1 (10,000 × 1 × 10⁻⁵).