AAT Bioquest

LC50 Calculator

LC50 is short for "lethal concentration 50%" or "median lethal concentration". It is the concentration of a substance (in air or water) at which half the members of a population are killed after a specified duration of exposure. Exposure is typically through inhalation. This value is very important in toxicology and agriculture as it gives an indication of substance (eg. herbicide) toxicity. The LC50 is inversely proportional to toxicity. A substance with a lower LC50 is more toxic than one which has a higher LC50.

Traditionally, the concentrations (x-value) are entered as mass of substance per volume of either air or solution. The units commonly used are milligram per liter (mg/L) or parts per million (ppm). The responses (y-value) are typically entered as percentage of population killed (range from 0 to 100). This will yield an upward-sloping sigmoidal curve. If percentage survival is used instead, a downward-sloping sigmoidal curve will be generated.

For technical assistance on using this calculator, please contact websupport@aatbio.com.

How to use this tool

1. 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:

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 LC50 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 LC50" button to display results, including calculations and graph.

Data Entry

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Have a question or a feature request about this tool? Feel free to reach out to us and let us know! We're always looking for ways to improve!

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This online tool may be cited as follows


"Quest Graph™ LC50 Calculator." AAT Bioquest, Inc.9 Dec2023https://www.aatbio.com/tools/lc50-calculator.


AAT Bioquest, Inc. (2023December 9). Quest Graph™ LC50 Calculator. AAT Bioquest. https://www.aatbio.com/tools/lc50-calculator.

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