IC50 / EC50 Nonlinear Regression Calculator
IC50 / EC50 Nonlinear Regression Calculator
Fit a four-parameter logistic dose–response model to estimate IC50, EC50, Hill slope, Top, Bottom and goodness-of-fit.
Model Settings
4-Parameter Logistic Model
Y = Bottom + (Top − Bottom) /
[1 + (X / EC50)^HillSlope]
IC50 / EC50 = concentration producing 50% of the fitted response range.
IC50 / EC50 = concentration producing 50% of the fitted response range.
The calculator uses nonlinear least-squares optimization.
Concentration is internally evaluated on a logarithmic scale
to improve stability across wide concentration ranges.
Experimental Data
| # | Concentration | Response |
|---|
IC50
—
Hill Slope
—
Top
—
Bottom
—
R²
—
RMSE
—
Data Points
—
Fit Status
Waiting
Enter experimental concentration/response data and click
Calculate Regression.
ŷ = b₀ + b₁x
ŷ = 8.44 − 0.55x
R² = 0.74 · b₀ = intercept · b₁ = slope ·
least squares minimizes squared vertical residual gaps.
least squares minimizes squared vertical residual gaps.
Focus
Data
Fitted line
Prediction
Residual
Drag a point to refit the line.
Drag any blue point
Animate
Tip: drag points vertically or horizontally. The regression line, R² and residuals update instantly.