ELISA Standard Curve Calculator

An ELISA Standard Curve Calculator plots absorbance readings against known concentrations to determine how much of a target molecule is in your unknown samples — a routine step in immunoassay lab work. Select your curve fitting model (Linear, Polynomial, or Four Parameter Logistic), enter your standard concentrations, dilution factor, and Optical Density (OD) readings per standard. The calculator returns your R² goodness of fit, curve equation, limit of detection, average CV%, and back-calculated concentrations for any sample OD values you provide.

Curve Fitting Model *

Number of Standards *

Standard Replications *

Sample Replications *

Highest Standard Concentration *

pg/mL

Dilution Factor *

Optical Density (OD) Data *

Enter OD readings for each standard, separated by spaces. One row per standard concentration.

Blank OD Value *

Sample OD Data (Optional)

Enter sample OD values to calculate concentrations. One row per sample.

Results

R² (Goodness of Fit)

Curve Equation

Average CV%

Limit of Detection

Samples Analyzed

Results Table

More Biology Tools

Frequently Asked Questions

What is the best curve fitting model for ELISA data?

The 4PL (Four Parameter Logistic) model is most commonly used for ELISA assays as it accounts for the sigmoidal shape of typical dose-response curves. Linear regression works well for narrow concentration ranges, while polynomial models can handle complex curves.

What is an acceptable R² value for an ELISA standard curve?

An R² value of 0.98 or higher is generally considered acceptable for ELISA standard curves. Values below 0.95 may indicate issues with the assay or curve fitting model selection.

How do I interpret the CV% values in my results?

CV% (Coefficient of Variation) measures the reproducibility of your replicates. CV values below 10% are excellent, 10-15% are acceptable, and above 20% may indicate pipetting errors or assay variability issues.

What should I do if my standard curve shows poor fit?

Try a different curve fitting model, check for outlier data points, ensure proper serial dilutions, and verify that your concentration range covers the samples' expected values. Consider using more standard points for better curve definition.

How many standard concentrations should I use?

Typically 6-8 standard concentrations provide adequate curve definition. More points (up to 11) can improve accuracy but require more reagents and time. Ensure standards span the expected sample concentration range.

What is the limit of detection (LOD) and how is it calculated?

LOD represents the lowest concentration that can be reliably detected above background noise. It's typically calculated as the blank OD plus 2-3 standard deviations of blank replicates, then back-calculated using the standard curve.

Can I use this calculator for other immunoassays besides ELISA?

Yes, this calculator works for any immunoassay that generates optical density or similar quantitative readouts, including CLIA, RIA, and other plate-based assays with standard curves.

How do I handle samples that fall outside the standard curve range?

Samples above the highest standard should be diluted and re-analyzed. Samples below the lowest standard may be below the limit of quantification and should be reported as such or the assay sensitivity improved.