AAT Bioquest

IgG Concentration Calculator

Immunoglobulin G (IgG) is the most common class of serum antibody. Antibodies of this class contain two identical heavy chains (50 kDa each) and two identical light chains (25 kDa each) for a total mass of 150 kDa. IgGs are particularly useful for their application in enzyme-linked immunosorbent assays (ELISAs).

The concentration of IgG in solution can be determined by substituting the molecular weight, extinction coefficient and λ max into a derived form of the Beer - Lambert Law. A substance's λmax is the wavelength at which it experiences the strongest absorbance. For IgG, this wavelength is 280 nm.

The absorbance at λmax can be measured using a spectrophotometer. There are some important things to keep in mind when measuring 280 absorbance:
  1. The IgG should be well-dissolved in solution. IgG precipitation will cause inaccuracies in concentration calculations.
  2. The absorbance reading should not exceed the maximum detection limit of the instrumentation. This can be identified by a plateau in the absorbance spectrum. If the absorbance spectrum plateaus, dilute the sample and try again.
  3. This calculator assumes a 1 cm pathlength for instrumentation. Standard cuvettes for spectrophotometers are typically 1 cm. If a different pathlength is used, value should be corrected during data entry.

How to use this tool

  1. Select the protein type. Or select "custom sequence" to enter the sequence.

  2. Enter the absorbance at λmaxPlease use the maximum absorbance as indicated by the spectrophotometric reading (ie. highest peak).

  3. If the absorbance is obtained with a diluted sample, enter the dilution factor in order to determine the concentration of the original sample.

  4. If pathlength differs from 1 cm, enter corrected value into pathlength textbox.

  5. Press calculate to display the concentration.

Data Entry

Absorbance at λmax
Dilution factor (optional)
Pathlength cm


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This online tool may be cited as follows


"Quest Calculate™ IgG Concentration Calculator." AAT Bioquest, Inc.1 Mar2024https://www.aatbio.com/tools/calculate-IgG-concentration.


AAT Bioquest, Inc. (2024March 1). Quest Calculate™ IgG Concentration Calculator. AAT Bioquest. https://www.aatbio.com/tools/calculate-IgG-concentration.