Perimeter measures the boundary length; area measures the surface enclosed. Trace the boundary before adding lengths. Internal shared edges do not contribute to the perimeter of a combined shape. **Figure** | **Perimeter** | **Area** Rectangle, length l and width w | 2(l+w) | lw Square, side s | 4s | s2 Circle, radius r | 2pi r | pi r2 Triangle, perpendicular height h to base b | Sum of three sides | 12bh Example A rectangle measures 7 cm by 4 cm. Its perimeter is 22 cm and its area is 28 cm2. A circle of diameter 10 cm has radius 5 cm, circumference 10pi cm, and area 25pi cm2. Convert squared units by squaring the length conversion: 1 m2=10,000 cm2. Thus 2500 cm2=0.25 m2, not 25 m².

Perimeter measures the boundary length; area measures the surface enclosed. Trace the boundary before adding lengths. Internal shared edges do not contribute to the perimeter of a combined shape.

A rectangle measures \(7\text{ cm}\) by \(4\text{ cm}\). Its perimeter is \(22\text{ cm}\) and its area is \(28\text{ cm}^2\). A circle of diameter \(10\text{ cm}\) has radius \(5\text{ cm}\), circumference \(10\pi\text{ cm}\), and area \(25\pi\text{ cm}^2\).

Convert squared units by squaring the length conversion: \(1\text{ m}^2=10\,000\text{ cm}^2\). Thus \(2500\text{ cm}^2=0.25\text{ m}^2\), not 25 m².

Figure	Perimeter	Area
Rectangle, length l and width w	\(2(l+w)\)	\(lw\)
Square, side s	\(4s\)	\(s^2\)
Circle, radius r	\(2\pi r\)	\(\pi r^2\)
Triangle, perpendicular height h to base b	Sum of three sides	\(\dfrac12bh\)

Boundary length and area

Boundary length and area