Molar Extinction Coefficient Calculator
Determine the molar extinction coefficient from absorbance and known concentration.
About Molar Extinction Coefficient Calculator
The extinction coefficient is intrinsic to a compound at a given wavelength and path length. Its magnitude sets the usable concentration range: a large ε gives sensitive detection but saturates at low concentration. Absorbance of 1.0 means only 10 per cent of light passes, which is why the linear range ends not far above it.
Formula
Molar Extinction Coefficient
ε = A ÷ (c l); transmittance = 10^(−A)
- ε
- Molar extinction coefficient, a property of the substance at a given wavelength
Worked example
With the default values below, Molar Extinction Coefficient Calculator returns Molar Extinction Coefficient of 41,000.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Measured absorbanceminimum 0
- 0.82
- Known concentrationminimum 0 mol/L
- 0.00002 mol/L
- Path lengthminimum 0.01 cm
- 1 cm
Results
- Molar Extinction Coefficient
- 41,000.00 M-1 cm-1
- Absorbance for a 1 M Solution
- 41,000.00
- Concentration Giving 0.05 Absorbance
- 0.0000012195 mol/L
- Concentration Giving 1.5 Absorbance
- 0.000036585 mol/L
- Transmittance
- 15.1356%
Step by step
- 1Values used
- 2Molar Extinction Coefficient
- 3Molar Extinction Coefficient= 41,000.00 M-1 cm-1
- 4Absorbance for a 1 M Solution= 41,000.00
- 5Concentration Giving 0.05 Absorbance= 0.0000012195 mol/L
- 6Concentration Giving 1.5 Absorbance= 0.000036585 mol/L
- 7Transmittance= 15.1356
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 10 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
How is Molar Extinction Coefficient calculated?
ε = A ÷ (c l); transmittance = 10^(−A) The extinction coefficient is intrinsic to a compound at a given wavelength and path length. Its magnitude sets the usable concentration range: a large ε gives sensitive detection but saturates at low concentration.
Why does Molar Extinction Coefficient matter?
Absorbance of 1.0 means only 10 per cent of light passes, which is why the linear range ends not far above it.
What values do I need to enter?
This calculator takes 3 inputs: Measured absorbance, Known concentration, Path length. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.