Enter your dose-concentration pairs and mortality percentages into the LD50/LC50 Calculator to find the lethal dose or concentration that kills 50% of a test population. Choose your Calculation Type and units to get the LD50/LC50 Value and Hill Slope.
LD50/LC50 Value
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Hill Slope
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R² Value
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Confidence Interval (Lower)
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Confidence Interval (Upper)
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LD50 (Lethal Dose 50) measures the dose of a substance that kills 50% of test organisms, typically given orally or by injection. LC50 (Lethal Concentration 50) measures the concentration in air or water that kills 50% of organisms through exposure.
You need at least 4-5 dose-response data points for reliable calculations. Include concentrations both above and below the expected LC50/LD50 value, and use log-spaced concentrations when possible.
The Hill Slope indicates the steepness of the dose-response curve. A steeper slope (higher absolute value) means a narrow range between no effect and maximum effect, while a shallow slope indicates a gradual response.
An R² value above 0.95 indicates excellent curve fit, while values between 0.90-0.95 are acceptable. Values below 0.90 suggest poor fit and may require additional data points or different analysis methods.
Confidence intervals show the range within which the true LD50/LC50 value likely falls. Narrower intervals indicate more precise estimates, while wider intervals suggest greater uncertainty in the measurement.
Common units include mg/L or ppm for aquatic toxicity, mg/kg for oral dosing, and μg/L for highly potent substances. Ensure all your dose values use the same unit for accurate results.
While this calculator is designed for mortality data (LD50/LC50), the mathematical approach is similar for IC50 (inhibitory concentration) or EC50 (effective concentration) if you substitute inhibition or effect percentages for mortality percentages.