Surface Area Calculator
Find surface area for boxes, cylinders, spheres, and cones.
Surface area
94 sq units
2(lw + lh + wh)
A sphere's neat fact
exactly 4× its shadow circle
Unfold it mentally
Surface area sums the faces: a box is three pairs of rectangles; a cylinder unrolls into a rectangle plus two circles; a cone unrolls into a circular sector plus its base. Spheres resist unrolling — Archimedes proved their 4πr² by comparison with the wrapping cylinder.
Why surface matters
Paint, wrapping, heat loss, and material costs all scale with surface, not volume. And because volume grows faster than surface as objects enlarge (the square-cube law), big things stay warm and small things dry out — biology and engineering both obey it.
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