Beer–Lambert Calculator
A = ε × l × c
Solve A = ε × l × c for absorbance, molar absorptivity, path length or concentration.
Inputs
Result
72.3473 µmol/L
Absorbance is dimensionless; ε, l and c must be dimensionally consistent.
Calculation
Beer-Lambert law
A = ε × l × c
Converted to canonical units
ε = 6220 L mol⁻¹ cm⁻¹, l = 1 cm, c = 7.23473 × 10^-5 mol/L
Rearranged and substituted
c = A / (ε × l)
A = 0.45
c = 72.3473 µmol/L
Inputs
- Absorbance
- 0.45
- ε
- 6220 L mol⁻¹ cm⁻¹
- Path length
- 1 cm
- Concentration
- —
No standard 1 cm cuvette is assumed — the path length used is the one entered above.
Extinction coefficients are substance-, solvent- and wavelength-specific and are never looked up automatically.
The linear Beer-Lambert relationship breaks down at high absorbance, with scattering samples, or where the analyte associates or dissociates with concentration.
About this calculator
The Beer–Lambert law states that absorbance is proportional to the molar absorptivity of the species, the optical path length and the concentration. Molar absorptivity is entered in L mol⁻¹ cm⁻¹ and path length is converted to centimetres internally.
No molar absorptivity is filled in for you: ε is wavelength-, solvent- and temperature-dependent, so use the value for your exact measurement conditions. The law holds only in the linear range of the instrument and for dilute, non-scattering samples.
LabCalc is provided as a calculation aid. Users remain responsible for verifying calculations, units, chemical compatibility, experimental procedures and applicable safety requirements before laboratory use.
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