Math & Statistics Calculator

Linear Interpolation Calculator

Estimate a value between two known points, calculate slope and intercept, solve the inverse x from y, and see whether the result is interpolation or extrapolation.

Known points

Calculates y at this x.
Calculates inverse x at this y.

Interpolation formula

The calculator uses y = y1 + (x - x1) x (y2 - y1) / (x2 - x1). This is the straight-line estimate between the two known points.

It also reports the slope and y-intercept so the line equation can be reused.

Practical uses

  • Estimate values from tables, charts or lab readings.
  • Fill missing values between two measurements.
  • Convert calibration points into a simple linear equation.

Linear Interpolation Calculator FAQ

What is linear interpolation?

Linear interpolation estimates a value between two known points by assuming the change between them is a straight line.

What is extrapolation?

Extrapolation means the target value is outside the known x range. The calculator still computes it, but uncertainty is higher.

Can this calculator solve for x from y?

Yes. Enter a target y value and it calculates the corresponding x when the line is not flat.

What formula does it use?

It uses y = y1 + (x – x1) x (y2 – y1) / (x2 – x1).