Torus Surface Area Calculator (A = 4π²Rr)

The calculator applies the exact formula A = 4π²·R·r. Worked example: R = 4 cm, r = 1 cm → A = 157.91 cm². Keep every input in one unit system and the result follows in square units (m², ft², cm²); full precision is kept until the final rounding. Radius fields expect radii — halve any diameter before entering it.

1. 1

   Enter the measurements

   Type the values required by the formula for torus surface area.

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

  Area scales with the square of linear dimensions

• 2

  Add overlaps and wastage before ordering material

• 3

  Paint coverage: 1 L covers roughly 10 m² per coat

• Mixing cm and m inputs — area then scales wrongly

• Using diameter as radius quadruples the result

• Forgetting flanges, rims and overlaps