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

How to use this tool1. 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 concentration per line.

Replicates can be graphed simultaneously. Graph will generated 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:

ConcentrationResponse 1Response 2...

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 value as well as the equation for the best fit line.

2. Verify your data is accurate in the table that appears.

3. Press the "Calculate " button to display results, including calculations and graph.

Process Data

This online tool may be cited as follows
MLA"Quest Graph™ EC50 Calculator." AAT Bioquest, Inc, 22 Oct. 2019,
APAAAT Bioquest, Inc. (2019, October 22). Quest Graph™ EC50 Calculator.". Retrieved from

This online tool has been cited in the following publications
Investigation of sun screening and antioxidant activity of M. indica ver “Willard”
Authors: De Silva, DSN ; B;ara, LL ; Samanmali, BLC ; Ratnasooriya, WD
Journal: Journal of Pharmacognosy and Phytochemistry (2019)
The cardenolides strophanthidin, digoxigenin and dihydroouabain act as activators of the human RORγ/RORγT receptors
Authors: Karas, Kaja ; Salkowska, Anna ; Walczak-Drzewiecka, Aurelia ; Ryba, Katarzyna ; Dastych, Jaroslaw ; Bachorz, Rafal A ; Ratajewski, Marcin
Journal: Toxicology letters (2018)
Biotransformation of estrone, 17β-estradiol and 17α-ethynylestradiol by four species of microalgae
Authors: Wang, Yuwen ; Sun, Qian ; Li, Yan ; Wang, Hongjie ; Wu, Kun ; Yu, Chang-Ping
Journal: Ecotoxicology and environmental safety (2019)