LD50/LC50 Calculator

The LD50/LC50 Calculator estimates the dose or concentration of a substance that kills 50% of a test population — a standard toxicity benchmark used in pharmacology, ecotoxicology, and chemical safety research. Select your calculation type (LD50 for lethal dose, LC50 for lethal concentration), choose your dose/concentration unit, and enter up to five dose/concentration and mortality % data point pairs. The calculator returns your LD50/LC50 value, along with Hill Slope, R² value, and upper and lower confidence interval bounds at your chosen confidence level.

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Results

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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Results Table

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Frequently Asked Questions

What is the difference between LD50 and LC50?

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.

How many data points do I need for accurate LD50/LC50 calculation?

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.

What does the Hill Slope represent?

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.

What is considered a good R² value for dose-response analysis?

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.

How should I interpret the confidence intervals?

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.

What units should I use for my dose-response data?

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.

Can I use this calculator for IC50 or EC50 calculations?

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.