MATH
Linear Interpolation Calculator
Estimate a value between two known points on a straight line.
Your result
MATHEnter your values and select calculate.
On this page How it works & practical examples
How to use the Linear Interpolation Calculator
Enter two distinct x endpoints and a target inside their closed interval. Reversing the endpoints leaves the interpolated value unchanged.
The calculation
y = y1 + (x−x1)(y2−y1)/(x2−x1)
Worked example
Between (0,0) and (10,100), x = 2.5 gives y = 25.
Assumptions and limits
Assumes a straight-line relationship only between the supplied points. Extrapolation beyond the interval is rejected; it does not infer a curve or uncertainty.
Common questions
Which inputs should I use?
Enter two distinct x endpoints and a target inside their closed interval. Reversing the endpoints leaves the interpolated value unchanged.
What does the result exclude?
Assumes a straight-line relationship only between the supplied points. Extrapolation beyond the interval is rejected; it does not infer a curve or uncertainty.