EC50 Calculator

EC₅₀ represents the concentration at which a substance exerts half of its maximal response. This value is particularly important in pharmacology, because it serves as an indication of drug potency. Traditionally, EC₅₀ is expressed as a molar concentration.

This calculator generates an EC₅₀ value typically thought of as the relative EC₅₀. For technical assistance on using this calculator, please contact websupport@aatbio.com.

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This online resource may be cited as follows

MLA	"Quest Graph™ EC50 Calculator." AAT Bioquest, Inc., 8 Oct. 2025, https://www.aatbio.com/tools/ec50-calculator.
APA	AAT Bioquest, Inc. (2025, October 8). Quest Graph™ EC50 Calculator. AAT Bioquest. https://www.aatbio.com/tools/ec50-calculator.
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Paste experimental data into the box on the right. Data can be copied directly from Excel columns. Data can also be comma-separated, tab-separated or space-separated values. If entering data manually, only enter one X-Value per line. Replicates can be graphed simultaneously. Graph will generate error bars based on the standard error of the mean (SEM). Simply paste or enter all data columns to begin. Format should be as follows:
Concentration Response 1 Response 2 …
C₁ R1₁ R2₁ …
C₂ R1₂ R2₂ …
C₃ R1₃ R2₃ …
… … … …
Users can graph up to three data sets on the same graph for comparison purposes. To add a new data set, press the "+" tab above the data entry area. Data sets can be renamed by double clicking the tab. Each dataset will generate a corresponding EC₅₀ value as well as the equation for the best fit line.
Verify your data is accurate in the table that appears.
Press the "Calculate EC₅₀" button to display results, including calculations and graph.

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Concentration	Response 1	Response 2	…
C₁	R1₁	R2₁	…
C₂	R1₂	R2₂	…
C₃	R1₃	R2₃	…
…	…	…	…

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