Beer-Lambert Law Calculator
Apply A = epsilon * l * c to determine unknown concentrations or expected absorbance values for solution measurements.
Concentration
0.0001 M
How to Use This Calculator
Provide extinction coefficient
Use a molar absorptivity in M^-1 cm^-1 obtained from literature or calibration standards.
Set the path length
Enter the optical path length of the cuvette or microplate well in centimeters.
Choose calculation mode
Select whether to solve for concentration from absorbance or calculate expected absorbance.
Review the results
Use the computed value for quantitative analysis or assay design. Units mirror your inputs.
Formula
A = epsilon * l * c
Rearranged for concentration: c = A / (epsilon * l). Keep units consistent so the resulting concentration matches your desired reporting units.
Example
Given epsilon = 15000 M^-1 cm^-1, l = 1 cm, and c = 1.2e-4 M, expected absorbance A = 15000 * 1 * 1.2e-4 about 1.80.
Full Description
The Beer-Lambert law links light absorption to concentration for homogenous solutions and enables quantitative spectroscopy in chemistry and biochemistry labs.
Accurate results require linear detector response, appropriate wavelength selection, and samples within the method's dynamic range.
Frequently Asked Questions
Can I use millimolar units?
Yes. Convert epsilon to match your concentration units or convert concentration to molar before applying the equation.
What path length should I use for microplates?
Estimate path length from well volume and geometry or use path length correction readings if supported by the instrument.
How do I handle baseline absorbance?
Subtract blank absorbance from the sample measurement before using the calculator.
What if the absorbance exceeds 2?
Dilute the sample or use a shorter path length to stay within the instrument's linear range.
Does scattering affect accuracy?
Yes. Highly scattering samples deviate from the Beer-Lambert law. Clarify samples or use techniques that compensate for scattering.