A weather app reports 70°F at noon and 80°F at 4 p.m. — your guess of 75°F for 2 p.m. is interpolation, the art of filling gaps between known points. In plain words, linear interpolation assumes the value changes at a steady rate between two measurements and picks the point proportionally along the way: halfway between the times gives halfway between the values. Scientists estimating a sensor reading between calibrations, appraisers valuing a house between two comparable sales, and animators smoothing motion between keyframes all interpolate. It is the honest middle ground between guessing and measuring — exact only when the true behavior really is a straight line.

This calculator performs the midpoint interpolation. Type the first known value into the Variable A box, say 70, and the second known value into the Variable B box, say 80. Read the interpolated middle value from the Result box: 75. For points that are not centered, weight the average by position yourself — but when the gap is symmetric, the simple midpoint is exactly right.

With the pre-filled defaults — Variable A 10, Variable B 5 — the Interpolation Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.