Area & Perimeter Calculator
Calculate area and perimeter for circle, rectangle, triangle, or square.
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FAQs
Why is π used in circle area calculations?
π (pi) is the ratio of a circle's circumference to its diameter — approximately 3.14159. It appears in circle formulas because circles are defined by their relationship to π. The area formula A = πr² can be understood by imagining the circle rearranged into a near-rectangle of height r and width πr.
How do I calculate the area of an irregular shape?
Break the irregular shape into regular sub-shapes (rectangles, triangles, circles) whose areas you can calculate separately, then add them together. Alternatively, the surveyor's formula or integration can handle complex irregular shapes. For land areas, GPS and GIS tools provide direct measurements.
What is the difference between area and surface area?
Area measures the 2D space enclosed by a flat shape. Surface area measures the total area of all faces of a 3D object — the amount of material needed to cover it. For example, the surface area of a cube with side s is 6s², while its volume is s³.