Beer-Lambert Law Calculator

Calculate

Absorbance Molar extinction coefficient (M⁻¹ cm⁻¹) Path length (cm) Concentration

How to use the Beer-Lambert law calculator

Choose what to calculate: absorbance, concentration, path length or molar extinction coefficient.
Type the other three values. The path length is usually 1 cm.
The answer appears with the transmittance.

Frequently asked questions

When does the law stop working?

At high absorbance, usually above about 1 to 2, where too little light reaches the detector. Dilute the sample and multiply back.

What is the formula?

A = ε × l × c: absorbance equals the molar extinction coefficient times the path length times the concentration.

How are absorbance and transmittance related?

A = −log₁₀ T. An absorbance of 1 lets 10% of the light through, and 2 lets 1% through.

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Exam courses

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Guides

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