Estimate the y-value at a chosen x by drawing a straight line between two known points.
Last updated: June 2026 | By Patchworkr Team
Linear interpolation estimates a value between two known points by assuming the segment between them is a straight line. The formula uses the slope of that line to calculate the missing y-value.
With points (1, 2) and (3, 6), the estimate at x = 2 is y = 4.
What if x1 and x2 are equal?
The slope is undefined when the x-values match, so the calculator rejects that input.
Does the calculator accept decimals?
Yes. Any finite real coordinate is accepted, including decimal and scientific notation values.
Is extrapolation allowed?
Yes. The same formula works when x is outside the interval, although it is then an extrapolation.
Can I leave a field blank?
No. Blank fields are treated as invalid instead of being silently converted to zero.
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