⚠️ Research Use Only. Not validated for clinical diagnostic use.
Dose-Response (4PL) Calculator
Fit 4-parameter logistic dose-response curves. Extract EC50, IC50, Hill slope, top, bottom, and R² from your data.
4-Parameter Logistic Fit
Enter dose/concentration and response pairs, one per line (e.g. "0.001 10"). Minimum 4 data points required.
Results
Bottom
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Top
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EC50 / IC50
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Hill Slope
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R²
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Fit Quality
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Understanding 4PL Parameters
| Parameter | Meaning |
|---|---|
| Bottom | Response at zero dose (asymptotic minimum) |
| Top | Maximal response (asymptotic maximum) |
| EC50 / IC50 | Concentration giving 50% of maximal effect |
| Hill Slope | Steepness of the curve (cooperativity) |
| R² | Goodness of fit — closer to 1 is better |
Frequently Asked Questions
What is a 4PL curve?
The 4-parameter logistic model: y = bottom + (top-bottom)/(1+10^((logEC50-x)*hillSlope)). It describes sigmoidal dose-response relationships.
What is EC50?
The concentration giving 50% of the maximal effect. For inhibition curves this is often reported as IC50.
What does R² mean?
Coefficient of determination. Values close to 1 indicate a good curve fit. Values below 0.9 suggest poor fit.
How many data points do I need?
Minimum 4 points. For reliable fits, use 6-8 points spanning the full curve including top and bottom plateaus.