How to use (3 steps)
- Select an example or enter [S] and v in the table (Excel paste OK).
- Confirm units and adjust advanced settings (weights, initial values) if needed.
- Km, Vmax, and plots (fit/residuals) are shown.
Linearization (e.g., Lineweaver–Burk) can distort error handling. Use nonlinear fitting as the main estimate and linearization as a reference.
Input ([S] and v)
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| [S]（—） | v（—） | Actions |
|---|
Blank rows are ignored. Enter values ≥ 0.
Paste (TSV/CSV)
Paste two columns ([S], v). A header row (S, v) is allowed.
Advanced settings
Initial values are guides for stable fitting. If it does not converge, try changing them.
Results (Km, Vmax)
Results will appear here.
——————SSE=—, RMSE=—, R²=—Outputs
Plots (fit & residuals)
Hover (or tap) a point to see details.
Per-point table
| [S] | v | v_fit | residual | residual² |
|---|
How it’s calculated
- Model:
v = (Vmax × [S]) / (Km + [S]) - Estimate Km and Vmax by minimizing the sum of squared residuals (nonlinear least squares).
- R² and RMSE are shown as guides to fit quality.
FAQ
How many points do I need to fit?
Because two parameters (Km and Vmax) are estimated, at least 3 points are recommended. More points usually improve stability.
The fit does not converge. What can I do?
Try adding high-concentration points, widening the [S] range, checking possible outliers, or changing initial values.
Is a high R² always correct?
It is a guide, but R² alone is not definitive. In nonlinear regression, R² can be negative if the fit is worse than a mean model. Check residual patterns and [S] range too.
Can I fit with different units?
Yes. Units are labels only; changing units does not convert entered values. Choose labels that match your numbers.
What is included in the share URL?
Settings (units, weights, bounds, initial values) and optionally input data.
Are my inputs sent anywhere?
All calculations run in your browser. Your data is not sent.
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