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Percentage Calculator
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Interpolation Calculator
Estimate a value between two known points with linear interpolation (or extrapolation).
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How to use this calculator
Enter your values. The result updates as you type; press Calculate to confirm and jump to the result on mobile. Use Share to send the calculator with your result.
Linear interpolation formula
y = y₁ + (x − x₁) × (y₂ − y₁) ÷ (x₂ − x₁)
It assumes a straight line between the two known points. Engineers use it to read between rows of steam tables, tax tables and charts. Example: (10, 100) and (20, 200), x = 14 → y = 140.
Frequently asked questions
What is extrapolation?
Using the same line to estimate outside the known range. It can be inaccurate if the relationship isn’t linear.
About this tool
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- Last updated
- 31 Oct 2026
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