ELISA 4PL/5PL Curve Fitter

Fit multi-concentration standard reference dilution values using symmetric 4-parameter logistic regression, examine curve residuals, and interpolate unknown cell sample concentrations locally.

Source: 4-Parameter Logistic Dose-Response EquationsSource: Symmetric Sigmoidal Assay Fitting Standards

Drop ELISA plate layout CSV file here (headers: sample, type, concentration, response)

Maximum file size: 5MB. All processing is 100% local inside your browser.

Quick Sandbox

Don't have a CSV file on hand? Click below to populate the workbench with a standard sandwich ELISA calibration curve.

Calibration Standards

Blank (0 Conc)

Unknown Samples

Interactive Standard Curve

Log10 concentration vs Response OD

Standards

Unknowns (Projected)

4PL Regression

Fitted Parameters (4PL)

R² (Goodness of Fit)0.99989

a (Min OD)-0.0219

d (Max OD)3.2234

c (EC50)331.5541

b (Hill Slope)1.0521

Interpolated Sample Concentration Results

Sample Name	OD (Response)	Interpolated Conc	Advisory Notes
Sample A1	1.550	312.401	Interpolated successfully
Sample A2	0.650	92.52	Interpolated successfully
Sample B1	0.080	12.737	OD outside strict standards bounds
Sample B2	2.850	2,304.63	OD outside strict standards bounds

Mathematical Formula & Assumptions

y = d + (a - d) / (1 + (x / c)^b)

Key Assumptions & Rules:

a represents the baseline signal asymptote (absorbance at concentration 0).
d represents the maximum plateau signal asymptote (absorbance at infinite concentration).
c corresponds to the inflection point / EC50, where half-maximal binding occurs.
b governs the steepness / Hill coefficient of the linear range.
Nelder-Mead downhill simplex algorithm performs least-squares regression locally on standard concentrations > 0.

Research Use OnlyThis calculator operates entirely in your browser. Verify calculations, reagent formulations, cell counts, and dilutions against your lab standard operating procedures (SOPs), supplier datasheets, and reference literature. Do not base medical diagnoses, clinical actions, or patient care decisions on this toolkit.