Surface Area Calculator

Surface area is the total area of all the outer faces of a 3D object, measured in square units (e.g. cm2, in2). It is how much material you would need to cover or wrap the shape completely — different from volume, which measures how much space it holds.

SA = 6 x s^2, because a cube has 6 identical square faces. A cube with side 5 has surface area = 6 x 25 = 150 square units. For a rectangular box the faces differ, so SA = 2(lw + wh + lh).

SA = 4 x pi x r^2. A sphere with radius 3 has surface area = 4 x pi x 9 = 113.10 square units. Note it is exactly 4 times the area of its own great circle (pi x r^2).

SA = 2 x pi x r x (r + h). This is the two circular ends (2 x pi x r^2) plus the curved side (2 x pi x r x h). A cylinder with radius 5 and height 10: SA = 2 x pi x 5 x 15 = 471.24 square units.

SA = pi x r x (r + l), where l is the slant height = sqrt(r^2 + h^2). This is the circular base (pi x r^2) plus the curved lateral surface (pi x r x l). A cone with radius 5 and height 10 has slant 11.18, so SA = pi x 5 x 16.18 = 254.16 square units.