Beer-Lambert Calculator
Calculate beer-lambert instantly in your browser — the published formula, worked locally with no data sent anywhere.
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What this tool does
Calculate beer-lambert instantly in your browser — the published formula, worked locally with no data sent anywhere. The law is linear only in dilute solutions — above an absorbance of about 1, molecular interactions and instrument stray light bend the calibration curve. ε is wavelength-specific; use the value at the measurement wavelength (usually λmax).
How to use the Beer-Lambert Calculator
- Enter or select solve for.
- Enter or select molar absorptivity ε (l/mol·cm).
- Enter or select path length (cm).
- Enter or select concentration (mol/l).
- Enter or select absorbance a (unitless).
- Read the calculated result; change any measurement to compare alternatives.
Formula
Beer–Lambert law: A = ε × l × c. Absorbance also converts to transmittance: %T = 100 × 10^(−A).
- solve
- Solve for
- epsilon
- Molar absorptivity ε (L/mol·cm)
- path
- Path length (cm)
- conc
- Concentration (mol/L)
- absorbance
- Absorbance A (unitless)
The law is linear only in dilute solutions — above an absorbance of about 1, molecular interactions and instrument stray light bend the calibration curve. ε is wavelength-specific; use the value at the measurement wavelength (usually λmax).
Worked example
For beer-lambert calculator, the following measurements illustrate the exact method: Solve for: absorbance; Molar absorptivity ε (L/mol·cm): 5000; Path length (cm): 1; Concentration (mol/L): 0.0001; Absorbance A (unitless): 0.5.
Inputs
- Solve forAbsorbance
- Molar absorptivity ε (L/mol·cm)5000
- Path length (cm)1
- Concentration (mol/L)0.0001
- Absorbance A (unitless)0.5
Result
- Absorbance A0.5
- Transmittance (%)31.62
Results explained
- Absorbance A
- Absorbance A from the formula above. The law is linear only in dilute solutions — above an absorbance of about 1, molecular interactions and instrument stray light bend the calibration curve. ε is wavelength-specific; use the value at the measurement wavelength (usually λmax).
- Transmittance (%)
- Transmittance (%) from the formula above. The law is linear only in dilute solutions — above an absorbance of about 1, molecular interactions and instrument stray light bend the calibration curve. ε is wavelength-specific; use the value at the measurement wavelength (usually λmax).
Frequently asked questions
Beer–Lambert law: A = ε × l × c. Absorbance also converts to transmittance: %T = 100 × 10^(−A).
The law is linear only in dilute solutions — above an absorbance of about 1, molecular interactions and instrument stray light bend the calibration curve. ε is wavelength-specific; use the value at the measurement wavelength (usually λmax).
Every field is labelled with its unit — enter values in exactly the labelled unit and read the result in the labelled output unit. Fields with a unit symbol also support the site-wide imperial/metric switch, which converts before the formula runs.
It uses double-precision arithmetic and the published constants and formulas named on this page. The last displayed digit may be rounded, and real conditions can differ from the idealized model described in the assumptions.
Yes. Every calculation runs entirely in your browser; nothing you enter is uploaded, stored or shared.