Top section: point-to-point interpolation. Bottom section: custom equations like y = 3x² + 2x - 4.
Known Points
Target Input
Linear Interpolation Result
Enter values to calculate...
Custom Equation Mode
Type y= or just the expression, using x as the variable. Use log(x) for base 10 and ln(x) for natural log.
Root Solver Information
The custom-equation root solver uses Regula Falsi (linear interpolation) with a fixed practical accuracy of 10^-15.
The iteration limit is fixed at 100.
This keeps the interface simple and avoids settings that do not improve results in JavaScript floating-point arithmetic.
Custom Equation Result
Enter an equation to calculate...
How to Use This Calculator (First-Time Users)
Enter your equation in the form of 3^x+3^-x-5, x^3-5x+2, sin(x), log(x), or similar. log means base 10, and ln means natural log.
To calculate Y from X, enter a value in Evaluate y at x. The calculator will immediately show the Y value.
To solve X for a known Y, leave the X field blank and enter the target value in Find x for y.
For reverse solving, give a sensible Range start and Range end that actually contain the answer.
Number of Intervals controls how finely the range is scanned before root solving begins.
Tolerance controls accuracy. Smaller tolerance means a stricter answer, but the solver may need more work.
The solver first scans for a sign change, then uses linear interpolation / Regula Falsi to narrow the answer.
If there are multiple roots in the selected range, all detected roots will be shown.
The table below the result shows the sampled x and y values for the chosen range.
If the answer is not found, widen the range or increase the number of intervals.