Free ELISA Calculator — OD to Concentration
Paste your plate reader export, fit a 4PL or 5PL standard curve, and get sample concentrations with replicate CV%, blank correction, LLOQ/ULOQ flags and CSV or PDF export. Everything runs in your browser — no account, no upload, no cost.
Data stays local
No upload and no account. Plate values are processed in the browser only.
4PL / 5PL fitting
Weighted logistic regression with R², residuals and automatic model selection.
Report-ready output
Replicate statistics, standard recovery, concentration platemap, CSV and PDF export.
How to calculate ELISA concentrations
- 1
Import the plate: paste a grid, a single column or a Well ID + value list, or upload .csv / .xls / .xlsx (48-, 96- and 384-well plates).
- 2
Assign wells: mark blanks, standards, samples and ignored wells on the interactive platemap; group replicates in one click.
- 3
Enter the standard series: type the top concentration and a dilution ratio and the series is filled automatically.
- 4
Fit the curve: choose 4PL, 5PL or automatic selection, with optional weighting and blank zero-anchor.
- 5
Review and export: check the Method Health panel (recovery, CV%, OD span, EC50 position) and export CSV or a PDF report.
Why not a spreadsheet?
Log-linear or point-to-point interpolation biases the low and high ends of a sigmoidal ELISA curve.
Blank correction, dilution factors and replicate CV% are easy to break when formulas are copied between sheets.
Spreadsheets rarely back-calculate the standards, so a failing curve looks fine on R² alone.
Labreador applies the same validated model to every plate and documents it with a citable DOI.
ELISA calculator FAQ
How does this free ELISA calculator work?
Paste or upload your plate reader export, mark blanks, standards and samples on the platemap, enter the standard concentrations, and the calculator subtracts the blank, fits a 4PL or 5PL standard curve and interpolates every sample concentration — including dilution factors and replicate statistics.
Is it really free and login-free?
Yes. There is no account, no trial and no upload limit. All calculations run locally in your browser, so your plate data never leaves your computer.
Which plate formats and file types are supported?
48-, 96- and 384-well plates. You can paste a grid, a single column, or a two-column Well ID + value list, or upload .csv, .xls and .xlsx exports.
Which curve fit should I use for ELISA?
Start with 4PL. Use 5PL when the standard curve is visibly asymmetric — the extra asymmetry parameter reduces bias at the plateaus. Labreador can also pick the better model automatically and reports R², residuals and back-calculated recovery for both.
Can I check whether my assay is valid?
The Method Health panel reports the R² quality tier, replicate CV%, back-calculated standard recovery (target 80–120%), OD span between top and bottom standards, EC50 position relative to the standard range and 95% CI width.