When to use this calculator
Convert a transmitted-light percentage into base-ten absorbance. Transmittance is a percentage of incident spectral radiant power.
Explore the absorbance & spectroscopy calculators for other questions in this topic. For a related calculation, use the Boyles Law Calculator: Find final volume for an ideal gas at constant temperature and fixed amount.
PUTTING IT INTO PRACTICE
Transmittance to Absorbance: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Transmitted fraction (%) | 10 |
| Result | 1 |
- Check the input labels and enter the example values above.
- Apply the relationship: Absorbance = −log₁₀(transmittance/100).
- The result is 1 , rounded for display.
How to interpret your result
Transmittance is a percentage of incident spectral radiant power.
Use consistent absorption-coefficient and path-length units. The linear Beer–Lambert relationship assumes appropriate spectral and sample conditions. Stray light, scattering, reactions and high concentration can invalidate a simple interpretation.
Frequently asked questions
Is absorbance the same as percent absorption?
No. Absorbance is a logarithmic ratio of incident to transmitted light; percent transmission and absorption are different quantities.
When is the transmittance to absorbance calculator useful?
Convert a transmitted-light percentage into base-ten absorbance. Transmittance is a percentage of incident spectral radiant power.
How do I use the transmittance to absorbance calculator?
Enter transmitted fraction (%). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Absorbance = −log₁₀(transmittance/100).
What should I check before using the result?
Transmittance is a percentage of incident spectral radiant power.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see IUPAC Gold Book: Beer–Lambert law ↗. This is a topic reference, not an external review or endorsement of this tool.
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