LD50 Calculator

LD₅₀ stands for "lethal dose 50%" or "median lethal dose". It is given with respect to ingestion of a substance after a specified amount of time and is the dose at which that substance kills half the members of a tested population. This value is very important in toxicology as it gives an indication of substance toxicity. The LD₅₀ is inversely proportional to toxicity. A substance with a lower LD₅₀ is more toxic than one which has a higher LD₅₀. For a database of LD₅₀ values for common compounds, please click here.

Traditionally, the doses (x-value) are entered as a ratio of the mass of the substance divided by the mass of the test subject. This corrects for differences in test subject body mass. The responses (y-value) are typically entered as percentage of population killed (range from 0 to 100). This will yield an upward-slopping sigmoidal curve. If percentage survival is used instead, a downward-slopping sigmoidal curve will be generated.

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

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References

This online resource may be cited as follows

MLA	"Quest Graph™ LD50 Calculator." AAT Bioquest, Inc., 16 Oct. 2025, https://www.aatbio.com/tools/ld50-calculator.
APA	AAT Bioquest, Inc. (2025, October 16). Quest Graph™ LD50 Calculator. AAT Bioquest. https://www.aatbio.com/tools/ld50-calculator.
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This online resource has been cited in 31 publications, including

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Nature (2025): 1--7

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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 LD₅₀ value as well as the equation for the best fit line.
Verify your data is accurate in the table that appears.
Press the "Calculate LD₅₀" 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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