ABSORBANCE – TRANSMITANCE CONVERTER

A = 2 - log10 %T

A spectrophotometer measures light transmittance through a material and from that absorbance can be inferred.  Transmittance and absorbance have a logarithmic relationship.  For example, a material transmitting 0.0001% would have an absorbance (optical density) of 6.  Use the tool below to easily convert between absorbance and transmittance.

Convert Transmittance to Absorbance
%T
A
Convert Absorbance to Transmittance
A
%T

Absorbance (optical density)

Light Transmittance %

0

100%

1

10

2

1

3

0.1

4

0.01

5

0.001

6

0.0001