Area & Perimeter Cheat Sheet

Area

The amount of space inside a 2D shape. Measured in square units (e.g., square inches, square meters).

Example: The area of a rug is the amount of floor it covers.

Perimeter

The total distance around the outside of a 2D shape. Measured in linear units (e.g., inches, meters).

Example: The perimeter of a fence is the total length of the fence.

Square Units

Units of area, such as square inches (in²) or square centimeters (cm²). A square with sides of 1 inch has an area of 1 square inch.

Example: A square with sides of 5 cm has an area of 25 cm².

Square - Area

Area = side × side = s²

Example: A square with a side of 4 cm has an area of 4 cm × 4 cm = 16 cm².

Square - Perimeter

Perimeter = 4 × side = 4s

Example: A square with a side of 4 cm has a perimeter of 4 × 4 cm = 16 cm.

Rectangle - Area

Area = length × width = l × w

Example: A rectangle with a length of 6 inches and a width of 3 inches has an area of 6 in × 3 in = 18 in².

Rectangle - Perimeter

Perimeter = 2 × (length + width) = 2(l + w)

Example: A rectangle with a length of 6 inches and a width of 3 inches has a perimeter of 2 × (6 in + 3 in) = 18 in.

Triangle - Area

Area = ½ × base × height = ½bh

Example: A triangle with a base of 8 cm and a height of 5 cm has an area of ½ × 8 cm × 5 cm = 20 cm².

Length Units

Common units: inches (in), feet (ft), yards (yd), miles (mi), centimeters (cm), meters (m), kilometers (km).

Example: A table is 3 feet long.

Area Units

Area units are length units squared: square inches (in²), square feet (ft²), square meters (m²), etc.

Example: A room is 100 square feet.

Conversion

Remember to use the same units when calculating area and perimeter. Convert if necessary.

Example: If the length is in feet and the width is in inches, convert one to match the other.