Mobile Quick Start
Build and fit your own equation in under a minute.
Paste data, adjust the equation, then run robust optimization with diagnostics.
Try: A*sin(B*x+C)+D | A*exp(B*x)+C | (A*x^2+B*x+C)/(D*x+E)
Custom Equation Curve Fitter
Tip: press Ctrl+Enter to run.
What This Tool Does
This is a custom equation curve fitting tool for nonlinear regression online. Enter your own equation, paste your X/Y data, and click run to get best-fit parameter values.
You can set parameter guesses and bounds to guide the fit. The page is built to handle difficult models and still stay responsive.
What makes it unique: you are not limited to preset equations. You can fit your own model, review fit quality with charts and diagnostics, and copy an Excel or Google Sheets formula in one step.
Data Readiness
Pending
Need at least 3 valid (x, y) rows.
Equation Readiness
Pending
Type or edit any equation with at least one parameter.
Run Readiness
Pending
Configure bounds and solver settings, then run.
Tip: Paste directly from Excel or CSV. Blank rows are ignored.
This field is fully user-adjustable. Type your own model anytime.
Custom Equation
y =
You are in custom mode. Parameter inputs below update automatically as you edit.
Ranked by commonality/frequency and tagged by equation type.
Quick presets:
Visual Preview:
`y = A*x^3+B*x^2+C*x+D`
For each parameter, provide an initial guess and bound range to stabilize difficult fits.
Parameter
Initial Guess
Lower Bound
Upper Bound
[ ] Data valid
[ ] Equation valid
[ ] Bounds valid
Optimizing with robust multi-start strategy...
Engine: Idle
Status: Waiting for input.
Fit Residuals (Error Distribution)
R-Squared
-
Adj. R-Squared
-
SSR
-
RMSE
-
AIC
-
BIC
-
Status
-
Parameter Confidence Diagnostics
| Parameter | Estimate | Std Error | 95% CI | t-Stat |
|---|