Ellipse Focus Distance Calculator (c = √(a²−b²))

The calculator applies the exact formula c = √(a² − b²), e = c/a. Worked example: a = 5, b = 3 cm → c = 4 cm, e = 0.8. Keep every input in one unit system and the result follows in length units (m, ft, cm); full precision is kept until the final rounding. Angles in radians pair with s = rθ; convert degrees with × π/180.

1. 1

   Enter the measurements

   Type the values required by the formula for ellipse focus distance.

2. 2

   Check the units

   One unit system throughout — cm, m, ft or in.

3. 3

   Read the result

   The calculator substitutes, evaluates and rounds only at the end.

• 1

  Keep angles in radians for s = rθ formulas

• 2

  1 rad = 57.2958°; degrees × π/180 = radians

• 3

  Unroll curved paths into straight segments to sanity-check

• Degrees entered where radians are required

• Using the chord length as the arc length

• Rounding π too early in chain calculations