Linear interpolation calculator
Interpolation between two points is the workhorse of reading any table that does not have your exact row.
Interpolated value
124
- Slope
- 6
- y-intercept
- 40
- Position between the points
- 0.4
- Outside the known range 1 means the answer is an extrapolation, which is far less trustworthy.
- 0
Show the working
- x1 = 10
- y1 = 100
- x2 = 20
- y2 = 160
- x to evaluate = 14
- Slope = 20 != 10 ? (160 - 100) / (20 - 10) : 0 = 6
- Interpolated value = 100 + 6 * (14 - 10) = 124
- Position between the points = 20 != 10 ? (14 - 10) / (20 - 10) : 0 = 0.4
- y-intercept = 100 - 6 * 10 = 40
- Outside the known range = (14 < min(10,20) || 14 > max(10,20)) ? 1 : 0 = 0
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- y = y1 + (x - x1) (y2 - y1) / (x2 - x1)