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Beer-Lambert Law Absorbance Calculator

The Beer-Lambert Law Absorbance Calculator computes light attenuation through absorbing solutions according to A = ε · b · c.

Extinction coefficient of the absorbing solute at measurement wavelength.

Internal optical path length of the cuvette (standard benchtop cuvettes are 1.0 cm).

Molar concentration of the dissolved chromophore in moles/liter.

Calculated Result
0.500A

Absorbance (A)

Transmittance (%T)

31.62%

Optical Density (OD)

0.500

Cuvette Path Length

1.00 cm

Extinction Coeff

1.00e+3 L/(mol·cm)

Calculation Breakdown

  1. Absorbance Calculation (A = ε × b × c)1000 L/(mol·cm) × 1 cm × 5.0000e-4 M = 0.5000
  2. Transmittance Conversion (%T = 100 × 10^(-A))100 × 10^(-0.5000) = 31.62%

Transmittance (%T) vs Absorbance (OD)

Interactive visualization based on your current inputs

Calculated Value
0.02550751000.0 A0.3 A0.6 A1.0 A1.5 A2.0 A

What Is the Beer-Lambert Law Absorbance Calculator?

The Beer-Lambert Law governs the linear relationship between light attenuation and the concentration of an absorbing chemical substance.

It provides the mathematical basis for quantitative UV-Vis spectrophotometry, colorimetric assays, and enzyme kinetics.

How Does the Beer-Lambert Law Absorbance Calculator Work?

Incident light of intensity I₀ passes through a solution; transmitted intensity I satisfies I = I₀ · 10^(-A).

The calculator multiplies molar absorptivity ε by path length b and molarity c to yield absorbance.

Transmittance is evaluated as %T = 100 · 10^(-A).

Beer-Lambert Law Absorbance Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

A = ε · b · c = -log₁₀(T)

Absorbance A equals molar absorptivity ε multiplied by cuvette path length b and solute molar concentration c.

How to Use the Beer-Lambert Law Absorbance Calculator

  1. Enter the substance extinction coefficient ε at your target wavelength.
  2. Enter your cuvette path length (typically 1.0 cm or 0.1 cm for microvolume readers).
  3. Enter solute molar concentration and view absorbance and optical transmittance.

Step-by-Step Example Calculation

Protein assay in 1 cm cuvette

Input Values:

molarAbsorptivity:1000
pathLengthCm:1
concentrationM:0.0005
Worked Steps: With ε = 1,000 L/(mol·cm), b = 1 cm, and c = 0.5 mM, optical absorbance is 0.500 (31.62% transmittance).

Understanding Your Result

Absorbance values between 0.1 and 1.0 reside within the linear instrumental precision range.

Absorbance greater than 1.5–2.0 indicates detector saturation where sample dilution is advisable.

Factors That Affect the Result

  • Wavelength: Extinction coefficients vary dramatically across the absorption spectrum.
  • Solvent and pH: Refractive index and ionization states shift chromophore absorptivity.

When Should You Use This Calculator?

  • Bradford, BCA, and NanoDrop protein concentration quantitation.
  • DNA/RNA purity and optical density assessment (A260/A280).

Assumptions & Limitations

  • Linear relationship holds for dilute solutions (< 10 mM) with monochromatic light.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Exact logarithmic attenuation according to Bouguer-Lambert-Beer formulation.

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