ELISA Data Analyzer
A free online ELISA data analyzer that fits 4-parameter logistic (4PL) curves to your standard data, back-calculates unknown sample concentrations, displays R² goodness of fit, and handles dilution factor corrections. View interactive standard curve plots with fitted lines — all processed in your browser with no experimental data uploaded.
Standard Curve Data
Unknown Samples
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What is an ELISA Data Analyzer?
An ELISA (Enzyme-Linked Immunosorbent Assay) data analyzer processes optical density (OD) readings from ELISA plates to determine analyte concentrations in unknown samples. It fits a 4-parameter logistic (4PL) curve to standard data points, then uses the fitted equation to back-calculate concentrations from measured absorbance values. The 4PL model accurately captures the sigmoidal dose-response relationship typical of immunoassays.
How to Use This Analyzer
- Enter your standard curve data: concentration and corresponding absorbance (OD) values
- Add unknown samples with their absorbance values and dilution factors
- Click Analyze to fit the 4PL curve and calculate concentrations
- Check the R² value to assess curve fit quality (>0.99 is excellent)
- View the standard curve plot and read back-calculated concentrations with dilution correction
Frequently Asked Questions
What is 4-parameter logistic (4PL) curve fitting?
4PL fitting models the sigmoidal relationship between concentration and response using four parameters: minimum asymptote (A), Hill slope (B), EC50 or inflection point (C), and maximum asymptote (D). The equation is: y = D + (A - D) / (1 + (x/C)^B). This model is the gold standard for ELISA and immunoassay data analysis because it accurately captures the S-shaped dose-response curve.
What R² value is acceptable for ELISA standard curves?
An R² value of 0.99 or higher is generally considered excellent for ELISA standard curves. Values between 0.95 and 0.99 are acceptable but may indicate some variability. Below 0.95 suggests poor curve fit, possibly due to pipetting errors, plate washing issues, or incorrect standard preparation. Always visually inspect the curve plot alongside the R² value.
Why are my unknown sample concentrations showing 'Out of Range'?
Samples show 'Out of Range' when their absorbance falls outside the standard curve range (below the lowest standard or above the highest standard). Extrapolation beyond the standard range is unreliable. Solutions: dilute high-concentration samples further and re-assay, or increase the standard curve range. Always include standards that bracket the expected sample concentrations.