Dose-Response Curve Calculator

A dose-response curve shows how a biological system reacts to increasing concentrations of a drug or compound — used in pharmacology and toxicology to find the concentration at which a substance produces half its maximum effect. Enter your concentration-response data pairs, select your concentration unit, response type, and curve type (EC50 or IC50) to get the fitted EC50/IC50 value. Secondary outputs include Hill Slope, R² value, and the top and bottom response plateaus from the four-parameter logistic curve fit.

Enter concentration and response values separated by comma, one pair per line

Use logarithmic scale for concentration axis

Results

EC50/IC50 Value

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Hill Slope

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R² Value

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Top (Max Response)

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Bottom (Min Response)

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Results Table

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Frequently Asked Questions

What is EC50 and how is it different from IC50?

EC50 is the concentration that produces 50% of the maximum effect, while IC50 is the concentration that produces 50% inhibition. EC50 is used for activation studies, IC50 for inhibition studies.

What data format should I use for the calculator?

Enter concentration and response values separated by commas, one pair per line. You need at least 4-6 data points spanning above and below the expected EC50/IC50 value for accurate curve fitting.

What does the Hill slope tell me about my dose-response curve?

The Hill slope indicates the steepness of the curve. A slope of 1 indicates a standard sigmoidal curve, while slopes >1 indicate cooperative binding and slopes <1 indicate negative cooperativity.

How is the R² value calculated and what does it mean?

R² measures how well the 4-parameter logistic model fits your data, ranging from 0 to 1. Values above 0.95 indicate excellent fit, while values below 0.8 suggest poor curve fitting.

Should I use logarithmic or linear concentration scale?

Logarithmic scale is recommended for most dose-response studies as it better displays the sigmoidal nature of the curve and is standard in pharmacology. Linear scale may be used for narrow concentration ranges.

What is the 4-parameter logistic equation used in this calculator?

The equation is: Y = Bottom + (Top - Bottom) / (1 + (X/EC50)^HillSlope). This models the sigmoidal dose-response relationship with four key parameters: top, bottom, EC50, and hill slope.

How many data points do I need for reliable EC50 calculation?

You need at least 4-6 concentration points, but 8-12 points provide better accuracy. Include concentrations both above and below your expected EC50 value, ideally spanning 2-3 orders of magnitude.

Can I use this calculator for different types of biological assays?

Yes, this calculator works for various assays including cell viability, enzyme inhibition, receptor binding, and drug efficacy studies. Simply select the appropriate response type and units.