What is Beer-Lambert Law?

The Beer-Lambert Law, also known as Beer’s Law, is a fundamental principle in spectroscopy that describes how light is absorbed by matter. This physical law states that the absorbance of light passing through a solution is directly proportional to both the concentration of the absorbing species and the path length of the light through the sample.

The law is expressed mathematically as A = εlc, where:

• A represents the absorbance (dimensionless)
• ε is the molar absorptivity coefficient (L⋅mol⁻¹⋅cm⁻¹)
• l is the path length of the sample (cm)
• c is the concentration of the absorbing species (mol/L)

How to Use Beer-Lambert Law Calculator

Step 1: Determine which variable you want to calculate (absorbance, molar absorptivity, path length, or concentration).

Step 2: Enter the known values in their respective input fields. Leave the field you want to calculate empty.

Step 3: Ensure your input values use the correct units:

• Molar absorptivity in L⋅mol⁻¹⋅cm⁻¹
• Path length in centimeters (cm)
• Concentration in moles per liter (mol/L)

Step 4: Click the calculate button to obtain your result.

Step 5: Review the calculated result and the explanation provided in the results box. The calculator will show the formula used and explain how the value was determined.

Step 6: For additional calculations, simply modify the input values as needed and calculate again. You can switch which variable you want to calculate by leaving that field empty and filling in the others.