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Math

Linear Interpolation Calculator

Estimate a y value between two known points and identify when a result is extrapolation.

Exact method explained belowEditable inputs

Set up your calculation

Runs on your device

SOLUTION

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter first point: x, first point: y, second point: x, second point: y, target x.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

y = y₁ + (x − x₁) × (y₂ − y₁) ÷ (x₂ − x₁). A target outside the two known x coordinates is extrapolation.

A WORKED EXAMPLE

Halfway between (0, 0) and (3, 4), x = 1.5 gives y = 2.

What to keep in mind

The relationship is assumed linear between the supplied points. Extrapolation is calculated but labeled because the same trend may not continue. Equal x coordinates are rejected.

Common questions

Can the known x values be in reverse order?

Yes. The calculation works in either order.

Is this a best-fit regression?

No. It connects exactly two points; it does not estimate a trend from a dataset.

Methodology maintained by ClarityKit. How these tools are built and checked.