Area of a Sphere Calculator
Calculate the surface area of a sphere from its radius using 4πr².
Step 1: Enter the radius of the sphere in the input field. Step 2: Select your unit of measurement (cm, m, inches, feet, etc.). Step 3: The calculator instantly computes the surface area using the formula 4πr². Step 4: Read the result in square units matching your input unit.
Surface Area = 4 × π × r², where r is the radius of the sphere. If you know the diameter instead, use r = d/2. π ≈ 3.14159265. For example, a sphere with radius 5 cm has surface area = 4 × π × 25 = 100π ≈ 314.16 cm².
A sphere is the three-dimensional shape formed by all points at the same distance from a fixed center. That constant distance is the radius, and it controls every other basic sphere property: diameter, volume, surface area, and the surface-to-volume ratio.
Surface area tells you how much outer skin the sphere has. In practical work, that matters whenever the outside of the object is what you care about: paint coverage, coating, heat exchange, evaporation, drag estimates, packaging, or any problem involving exposure at the boundary.
Among closed 3D shapes with the same volume, the sphere has the smallest surface area. That is why bubbles, droplets, and many biological cells naturally tend toward spherical forms when surface energy matters. It is also why small spheres behave so differently from large ones: as radius shrinks, the surface-to-volume ratio rises quickly.
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