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Absorbance calculator

Here you can calculate absorbance or concentration of unknown solution using Beer-Lambert's law. Enter values of any three parameters and you can get the value of fourth parameter by simple click.

Calculate Absorbance

Select units of concentration

Absorbance in spectroscopy

When an electromagnetic radiation (EMR) such as UV or visible light falls on matter, it can undergo many types of changes in its pathway depending on the nature of material. It can undergo reflection, refraction, scattering and transmission. In the last process, light travels through the matter with absorption of energy by the medium. This process is called absorption and it can be measured by using Beer-Lambert’s law.

absorption process

Beer-Lambert law

Beer-Lambert law gives a quantitative relation between absorbance of UV-visible radiation by the analyte to its concentration. According to this law, absorbance of EMR is directly proportional to both concentration and thickness of the analyte through which radiation passes.

Beer-Lambert law

This law can be stated in another way. The intensity transmitted radiation reduces exponentially with both concentration of the analyte and path length of electromagnetic radiation.

exponential form

How to use this calculator?

With this calculator, absorbance can be calculated readily with simple click. For this sufficient data is to be entered into the corresponding blocks. Enter the values of absorptivity, pathlength, concentration of the analyte and click calculate button to get the result.

Calculate concentration

Units of concentration can be selected as moles per liter (Molar) or gram per 100 ml. Based on the selection of proper units for concentration, units for absorptivity will be expressed.

Multiple use of calculator

If you want to calculate any parameter in the Beer-Lambert law, just enter values of other three parameters and click to calculate. The result will be displayed with proper units for the calculated parameter .

calculate absorptivity

Units of parameters

Units of absorptivity depend on how the term concentration is expressed. Suppose concentration is measured in moles per liter then absorptivity is termed as molar absorptivity and expressed in the units of lit.mol-1.cm-1 .

Molar absorptivity

On the other hand, if concentration is expressed in gram per 100 ml or %w/v , then units of absorptivity is expressed as dl.gm-1.cm-1