Circle Calculator: Area, Circumference, Radius & Diameter

Circles are everywhere — from pizza to planets. Understanding how to calculate circle properties is one of the most useful math skills.

Circle Formulas

Examples

Pizza Size Comparison (12" vs 16")

A 12-inch pizza has radius 6 in

• Area = π × 6² = 113 sq in
• Circumference = 2π × 6 = 37.7 in

A 16-inch pizza has radius 8 in

• Area = π × 8² = 201 sq in
• Circumference = 2π × 8 = 50.3 in

👉 The 16" pizza is 78% larger than the 12" — but usually costs only 30-40% more! That's value.

Real-World Circle Calculations

• Gardening: How much mulch for a circular flower bed
• Construction: Concrete for a round patio
• Cooking: Adjusting circular pan recipes
• Design: Estimating material for circular signs

Try Our Circle Calculator

Our Circle Calculator computes all properties:

• Area, circumference, radius, and diameter
• Enter any one value to find the rest
• Uses π to 15 decimal places for accuracy

💡 Fun Fact: If you know the circumference of a tree trunk, divide by π (3.14) to get its diameter — a standard forestry technique!

*Calculate circle properties with our free Circle Calculator.*