How to Find the Radius of a Sphere

Many people wince at the thought of calculating math formulas, dreading a return to this nemesis of their High School days. However, though you may never need to apply math formulas in many occupations, there are a number of formulas that are always handy to learn and remember. The radius of a sphere is the length of the center point to the outside edge. You may encounter this formula if purchasing replacement pool or billiard balls; fortunately the formula is simple and easily worked out using a calculator.

Things You'll Need

• Ruler or tape measure
• Pencil
• Paper
• Calculator

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Instructions

1. • 1

     Measure the distance of the sphere from edge to edge. Ensure the ruler or tape measure crosses the center point of the sphere. This figure will give you the diameter of the sphere.

   • 2

     Jot down on a piece of paper the figure you measured in Step 1.

   • 3

     Divide the diameter length by two. Use the calculator if it is a long number. The result is the radius of the sphere, as the diameter is always double the radius. The formula is written down as 2R = D.