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🌈 UV Spectroscopy Calculator

Beer-Lambert Law, Molar Absorptivity and Transmittance ↔ Absorbance converter — all in one page.

Beer-Lambert Law

A = ε × c × l

A — Absorbance

ε — Molar Absorptivity (L·mol⁻¹·cm⁻¹)

c — Concentration (mol/L)

l — Path Length (cm)

Transmittance ↔ Absorbance Converter

A = −log(T) T = 10^(−A)

Enter Absorbance (A)

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Enter Transmittance (T, 0–1 or %)

Type a value in either field to convert

LOD & LOQ Calculator (ICH Q2(R1))

LOD = 3.3σ/S LOQ = 10σ/S

σ — Std Dev of Response

S — Slope of Calibration Curve

LOD

LOQ

📖 Example (Beer-Lambert): ε = 6,220 L mol⁻¹ cm⁻¹, path length = 1 cm, absorbance = 0.310 → concentration = 0.310 ÷ (6220 × 1) = 4.98 × 10⁻⁵ mol/L. Cite as: "Concentration determined by UV absorbance at 260 nm using Beer-Lambert law (Scitero UV Spectroscopy Calculator, scitero.com)."

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Beer-Lambert

Solve for any variable — absorbance, concentration, molar absorptivity or path length.

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Instant conversion

Type in either field — Transmittance ↔ Absorbance converts as you type.

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⚠️ Verify before use: Beer-Lambert assumes dilute solutions with no scattering or chemical interactions affecting absorbance. Double-check critical results independently, especially near the edges of your instrument's linear range.

✔ Formulas last verified against primary references: March 2025 · Report an error

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Beer-Lambert law: practical application in analytical labs

Beer-Lambert law (A = εcl) is the foundation of UV-Vis spectrophotometry. To apply it: measure absorbance at the analyte's wavelength maximum, use a 1 cm path length cuvette, and know ε from literature or a calibration curve. Linear range is typically A = 0.05–1.0; above A = 1.0 stray light causes detector non-linearity. For nucleic acids: DNA at 260 nm, ε ≈ 6600 L mol−1 cm−1 per base pair. LOD = 3.3σ/S and LOQ = 10σ/S per ICH Q2(R1), where σ is the residual standard deviation of the regression and S is the slope.