Beer Lambert Law Calculator

Work out beer lambert law instantly with clear inputs, formula shown and shareable results.

About Beer Lambert Law Calculator

Beer-Lambert says absorbance is the product of molar absorptivity, path length and concentration, so it rises linearly with how much absorber the beam crosses. Transmittance is the exponential counterpart, 10 to the power of minus absorbance. An absorbance of 0.75 passes 17.8% of the light, which is why absorbance rather than transmittance is used for calibration lines.

Formulas

Beer-Lambert law

A = epsilon x l x c

Transmittance

T = 10^-A

Worked example

With the default values below, Beer Lambert Law Calculator returns Absorbance of 0.7500. Change any input above and every figure here is recalculated in your browser.

Inputs used

Molar absorptivityminimum 0 L/(mol cm): 15,000 L/(mol cm)
Cuvette path lengthminimum 0 cm: 1 cm
Concentrationminimum 0 mol/L: 0.00005 mol/L

Results

Absorbance: 0.7500
Transmittance: 0.17783
Percent Transmittance: 17.78%
Light Absorbed: 82.22%

Step by step

1Values used
2Beer-Lambert law
3Transmittance
4Absorbance= 0.7500
5Transmittance= 0.17783
6Percent Transmittance= 17.78
7Light Absorbed= 82.22

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does absorbance stop being linear at high concentration?

Above about A = 2 stray light and molecular interactions dominate, and the beam is attenuated so heavily that detector noise takes over. Dilute into the 0.1-1 range.

What does a molar absorptivity of 15,000 mean?

A strongly absorbing species. Values run from a few tens for weak transitions to over 100,000 for intense charge-transfer bands.