Beer-Lambert Law Calculator

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Calculate the relationship between absorbance and concentration of a substance in a solution.

Solve For

Parameters

Molar Absorptivity (ε)

L/(mol·cm)

Path Length (l)

Concentration (c)

mol/L

Calculation Results

Enter parameters to calculate the missing value

About this calculator

Overview

The Beer-Lambert Law explains how light gets absorbed as it travels through a solution. It's the science behind why darker tea is stronger, and it powers critical technology like pulse oximeters that check your oxygen levels by shining red light through your finger.

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Pro Tips

Absorbance has no units! It's a ratio of light intensity.
Molar absorptivity (ε) is a unique 'fingerprint' for every chemical at a specific wavelength.
Path length is usually 1 cm in standard lab cuvettes.
Always blank your spectrophotometer with pure solvent first.
If your absorbance is > 1.0, dilute your sample for better accuracy.

Fun Facts

"Pulse oximeters use this law to measure your blood oxygen levels! They compare the absorption of red and infrared light by hemoglobin."
"Forensic scientists use it to determine the exact concentration of poisons or drugs in blood samples."
"The law combines discoveries by three different scientists: Pierre Bouguer (who noticed light fades in the atmosphere), Johann Lambert (who did the math), and August Beer (who related it to concentration)."
"Atmospheric scientists use it to measure ozone layer thickness and protect us from UV radiation."
"Industrial food safety relies on it to ensure the exact amount of food coloring is used in your favorite drinks."
"At very high concentrations, the law stops working because crowded molecules start interacting with each other, changing how they absorb light."
"Astronomers use a version of this law to figure out what stars and other planets are made of by analyzing the light passing through their atmospheres."

Formula: A = ε × l × c