Area & Perimeter Calculator
Calculate the area and perimeter of common 2D shapes — rectangle, square, circle, and triangle.
Formulas used
- Rectangle — Area = length × width; Perimeter = 2 × (length + width)
- Square — Area = side²; Perimeter = 4 × side
- Circle — Area = π × radius²; Circumference = 2 × π × radius
- Triangle — Area = ½ × base × height; Perimeter = sum of all three sides
Worked example
A circle with radius 7 has an area of π × 7² ≈ 153.94 square units and a circumference of 2 × π × 7 ≈ 43.98 units.
Frequently asked questions
What's the difference between area and perimeter?
Area measures the space enclosed inside a shape (in square units). Perimeter (or circumference for a circle) measures the total length of the shape's boundary (in linear units).
Why does the triangle need both a height and two extra sides?
The height is needed to calculate area (½ × base × height), but the perimeter requires the actual lengths of all three sides, which isn't always derivable from just the base and height alone.