Absorbance converter
Convert absorbance to percent transmittance and back. An absorbance of 1 lets exactly a tenth of the light through.
That's 3.2× as dark as the best measuring range, while a strongly colored sample is 10× darker. About 10% of the light gets through.
What it means
How much light gets through?
Above about 2 the detector is measuring very little light, and stray light dominates. Dilute the sample rather than trusting the reading.
Every unit
Your absorbance in every unit
Learn
Three things worth knowing
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Each unit of A is a tenfold cut
A = 0.3 is about half the light, A = 1 is a tenth, A = 2 a hundredth. Doubling the concentration doubles the absorbance but squares the transmittance: 10% of the light becomes 1%.
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Beer–Lambert, once more
Absorbance is concentration times path length times the extinction coefficient. Taking the logarithm is exactly what turns a multiplying law into an adding one.
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Aim for the middle
The best precision is around A = 0.5. Below 0.1 the difference from the blank is noise; above 2 almost nothing reaches the detector.
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Popular absorbance conversions
Background
About absorbance
Transmittance is the fraction of light that gets through. Absorbance is its negative logarithm, and that is the quantity worth measuring: absorbance is proportional to concentration, transmittance is not.
A = 1 means 10% gets through, A = 2 means 1%, A = 3 means a tenth of a percent.