# Linear interpolation and extrapolation

## Calculator

This calculator allows you to obtain by linear interpolation or extrapolation a value from two other pairs of values. Enter the two known points and the known value (X or Y) of the third point. The result will be automatically calculated, together with a graph and the equation to show how to make the calculation:

X Y
Variable
name
Known points:
Point 1
Point 2
Point to calculate:
Point 3

## Theory

The calculation is carried out considering that the function that relates the values of both axes is linear This is true for many real applications, however many physical phenomena do not fulfill a linear relationship between their variables. In those cases, linear interpolation or extrapolation is still very useful since it allows us to obtain an approximate intermediate value for a series of points.

Interpolation: We have two points represented by the two pairs of values (x1, y1) and (x2, y2). We want to calculate an intermediate point, for which we have one of the values, x3 or y3.

Extrapolation: It is similar, but now the third point we know that it is not between point 1 or 2, but has higher or lower values.