1. What is Circle Area?

The area of a circle is the space contained within its circumference. It's measured in square units (square feet in this calculator) and is fundamental in geometry, construction, landscaping, and many other fields.

2. How Does the Calculator Work?

The calculator uses the circle area formula:

Where:

• \( \pi \) — Mathematical constant (~3.14159)
• \( r \) — Radius of the circle (distance from center to edge)

Explanation: The area increases with the square of the radius, meaning doubling the radius quadruples the area.

3. Practical Applications

Details: Circle area calculations are used in determining material quantities for circular projects (pools, patios), calculating coverage for circular areas (lawn care, painting), and in engineering designs (pipes, tanks).

4. Using the Calculator

Tips: Measure the radius in feet (half the diameter). For irregular shapes, approximate as a circle or break into multiple circles. Ensure radius is positive.

5. Frequently Asked Questions (FAQ)

Q1: What if I only know the diameter?
A: Divide the diameter by 2 to get the radius before using the calculator.

Q2: How precise is π in the calculation?
A: The calculator uses PHP's built-in M_PI constant which is precise to about 14 decimal places.

Q3: Can I use this for metric units?
A: Yes, but ensure all measurements are in the same units (e.g., meters for radius gives m²).

Q4: Why does area increase so rapidly with radius?
A: Because area depends on radius squared - this is a fundamental geometric property of circles.

Q5: How to calculate area of a semicircle?
A: Calculate full circle area then divide by 2.