Absorbance To Concentration Calculator

Work out absorbance to concentration instantly with clear inputs, formula shown and shareable results.

About Absorbance To Concentration Calculator

Reading a concentration off a spectrophotometer inverts Beer-Lambert: c = A/(epsilon x l). An absorbance of 0.75 in a 1 cm cell with molar absorptivity 15,000 corresponds to 5.0e-5 mol/L, or 50 micromolar. Accuracy is best between absorbance 0.1 and 1.0, so the calculator flags readings outside that band.

Formulas

Inverted Beer-Lambert

c = A / (epsilon x l)

Transmittance check

%T = 100 x 10^-A

Worked example

With the default values below, Absorbance To Concentration Calculator returns Concentration of 5.0000 × 10⁻⁵. Change any input above and every figure here is recalculated in your browser.

Inputs used

Measured absorbanceminimum 0: 0.75
Molar absorptivityminimum 0 L/(mol cm): 15,000 L/(mol cm)
Cuvette path lengthminimum 0 cm: 1 cm

Results

Concentration: 5.0000 × 10⁻⁵ mol/L
Same Concentration In Micromolar: 50.000
Percent Transmittance: 17.78%
Measurement Quality: Within the reliable 0.1-1.0 absorbance window

Step by step

1Values used
2Inverted Beer-Lambert
3Transmittance check
4Concentration= 0.0001 mol/L
5Same Concentration In Micromolar= 50.000
6Percent Transmittance= 17.78
7Measurement Quality= Within the reliable 0.1-1.0 absorbance window

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 4 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

What if I do not know the molar absorptivity?

Build a calibration line from standards instead: the slope is epsilon times the path length, so the unknown reads straight off the graph.

Does a longer cuvette help with dilute samples?

Yes. A 10 cm cell multiplies absorbance tenfold, which is a standard trick for trace analysis.