Interpolation Calculator

Linear interpolation is a method of estimating an unknown value that falls between two known data points by assuming the relationship between them is a straight line. The formula calculates where the target X would land on that line to produce a corresponding Y value.

The calculator uses the standard linear interpolation formula: Y2 = Y0 + (X2 − X0) × (Y1 − Y0) / (X1 − X0). This finds the proportional Y value at your target X based on the slope between the two known points.

Yes. If your target X2 falls outside the range of X0 and X1, the calculator will extrapolate — extending the line beyond the known points. Keep in mind that extrapolation assumes the linear trend continues, which may not be accurate for all real-world data.

If X0 equals X1, the denominator in the interpolation formula becomes zero, making the calculation undefined. Make sure your two known X values are different to get a valid result.

You need four known values — X0 and Y0 for the first data point, and X1 and Y1 for the second data point — plus the target X2 for which you want to find the estimated Y2.

Linear interpolation assumes a straight-line relationship between two points, which works well when data changes gradually and uniformly. For curved or rapidly changing data, more advanced methods like polynomial or spline interpolation may give better results.

Interpolation is widely used in engineering (reading values from lookup tables), finance (estimating rates), meteorology (weather modeling), computer graphics (smooth animations), and scientific data analysis where measurements exist only at discrete points.

Yes. If the trend between your two known points decreases and your target X is beyond the lower-valued point, the interpolated Y2 can be negative. The formula handles negative values correctly as long as your inputs are valid.