Extrapolation Calculator
Linear extrapolation beyond two known points.
Enter your values
ⓘ Live results
Results
- Extrapolated y
- 21
- Slope
- 2
- Equation
- y = 2x + 1
- Type
- Extrapolation (outside the data)
Quick answer
Linear extrapolation extends the straight line through two known points: y = y₁ + (x − x₁) × (y₂ − y₁) ÷ (x₂ − x₁).
y = y₁ + (x − x₁)(y₂ − y₁)/(x₂ − x₁)
How to use the Extrapolation Calculator
- 1Enter the first known point.
- 2Enter the second known point.
- 3Enter the x you want to project to.
Worked example
Using the values the calculator loads with:
Inputs
- x₁1
- y₁3
- x₂4
- y₂9
- Target x10
Results
- Extrapolated y21
- Slope2
- Equationy = 2x + 1
- TypeExtrapolation (outside the data)
Frequently asked questions
Is extrapolation reliable?
Only near the data range — the further you go beyond it, the more the straight-line assumption can break down.
What's the difference from interpolation?
Interpolation estimates inside the known range; extrapolation projects outside it.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.