Linear Interpolation Calculator
Math
Estimate a value between two points on a straight line.
Formula
y = y₁ + (x−x₁)(y₂−y₁)/(x₂−x₁)
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Targets outside the two x coordinates use linear extrapolation.
Example Calculation
Example inputs
- x₁: 0
- y₁: 0
- x₂: 10
- y₂: 20
- Target x: 3
Between (0,0) and (10,20), x=3 gives y=6.
Frequently asked questions
How do I use this calculator?
Enter x₁, y₁, x₂, y₂, target x. The result updates automatically. Use Reset to restore the example values.
What method does it use?
y = y₁ + (x−x₁)(y₂−y₁)/(x₂−x₁). Targets outside the two x coordinates use linear extrapolation.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.