Circle Area Calculator

Where r is the radius of the circle.

Calculate the area of a circle with radius 5 cm:

Result: 78.54 cm²

1. Enter the radius of the circle
2. Click "Calculate" to see the area

• Circumference: $2 \\pi r$
• Diameter: $2r$
• Area from diameter: $\\frac{\\pi d^2}{4}$

• Calculating land area
• Design and manufacturing
• Physics and engineering
• Architecture and construction
• Graphics and design

What is π (pi)? Pi is the ratio of a circle's circumference to its diameter, approximately 3.14159265.

Can I calculate the area of a semicircle? Yes, divide the full circle area by 2.

How do I find the radius from the area? $r = \\sqrt{\\frac{\\text{area}}{\\pi}}$

What units should I use? Any consistent unit (meters, feet, inches, etc.). The area will be in square units.

Is the formula accurate? Yes, it's mathematically exact. Use sufficient precision for π in your calculations.