Linear interpolation calculator
Estimate a value between two points assuming a straight-line relationship.
How do I use this page?
- Enter values or use the example in the form.
- Choose a mode or units where available.
- Read the result and check the calculation steps below.
What this page does not do: x₁ and x₂ must differ. No extrapolation outside the interval; the tool does not establish that your data are linear.
Further reading
Theory — what is linear interpolation?
Linear interpolation estimates a value between two known points, assuming the relationship between them follows a straight line. For example, between points (0,10) and (10,30), the value at x=5 equals y=20 — the formula distributes the total change in y proportionally to the position of x between the endpoints. The method works well when the real relationship is approximately linear; for data with noticeable curvature, the interpolated result can differ significantly from the actual value.
Frequently asked questions
How is the result calculated?
What are the limitations?
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