What is the formula for the surface area of a sphere?

The surface area of a sphere is given by S = 4πr², where r is the radius and π ≈ 3.14159265. This formula means the surface area is exactly four times the area of a great circle of the sphere.

What units does the result use?

The result is expressed in the square of whatever unit you enter the radius in. For example, if the radius is in centimeters, the surface area is in cm². The calculator labels the output unit automatically.

Can I enter the diameter instead of the radius?

This calculator takes the radius as input. If you know the diameter, divide it by 2 to get the radius before entering it.

How accurate is the result?

The calculation uses JavaScript's built-in Math.PI constant (approximately 3.141592653589793) and displays results rounded to 6 significant figures, which is sufficient for virtually all practical purposes.

What is the surface area of a unit sphere (radius = 1)?

A sphere with radius 1 has a surface area of 4π ≈ 12.5664 square units. You can verify this by entering 1 in the calculator.

Surface Area of a Sphere Calculator

Enter a sphere radius and instantly get the surface area using the formula 4πr², with unit conversion support.

Sphere Radius

Radius

Unit

Formula

S = 4 × π × r²

where r is the radius of the sphere

Enter a radius and click Calculate

Summary

This calculator computes the surface area of a sphere from its radius using the standard formula 4πr². Simply enter the radius and choose your unit of measurement — the result is displayed instantly with full precision. You can also switch between common units such as millimeters, centimeters, meters, inches, and feet.

How it works

Enter the radius of the sphere in the input field.
Select the unit of measurement (mm, cm, m, in, or ft).
The calculator applies the formula Surface Area = 4πr².
The result is displayed in the same unit squared (e.g. cm²).
Use the Copy button to copy the result to your clipboard.

Use cases

Calculate the surface area of a ball for a physics or engineering problem.
Determine how much material is needed to coat or wrap a spherical object.
Verify geometry homework answers involving sphere surface area.
Estimate paint or insulation coverage for spherical tanks or domes.
Convert between unit systems when working with sphere dimensions.
Use in classroom demonstrations of the 4πr² formula.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu