What is the calculation for converting between percent transmittance and absorbance?

Document ID

Document ID TE780

Published Date

Published Date 11/06/2018
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Question
What is the calculation for converting between percent transmittance and absorbance?
Summary
Convert between percent transmittance and absorbance
Answer
To convert a value from percent transmittance (%T) to absorbance, use the following equation: Absorbance = 2 - log(%T). For example to convert 56% T to absorbance calculate 2 - log(56) = 0.252 absorbance units.

To convert a value from absorbance to percent transmittance, use the following equation: %T = antilog (2 - absorbance). For example to convert an absorbance of 0.505 to %T calculate antilog (2 - 0.505) = 31.3 %T.

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