How to use the rectangle calculator
Calculate the area and perimeter of a rectangle using its width and height. Match the on-screen corners to a small rectangular object, or enter dimensions that you already know. Calibrate your display before using the shape for direct physical measurements.
Rectangle area and perimeter formulas
Area equals width × height. Perimeter equals 2 × (width + height). A rectangle 8 cm wide and 4.5 cm high has an area of 36 cm² and a perimeter of 25 cm. Check the squared unit when comparing areas.
Fit a rectangle to an object
Drag the upper-left and lower-right handles to align the rectangle with the outside edges of your object. Drag inside the shape to move it without changing its dimensions. The width and height fields also let you construct a specific reference size.
Understand squared-unit conversions
One inch is 2.54 cm, but one square inch is 6.4516 cm². Area conversion uses the square of the length conversion factor. Switching the toolbar unit converts the length and area readings consistently.
A few common questions
Can I calculate the area of a square?
Yes. Enter the same width and height. A square with sides of 5 cm has an area of 25 cm² and a perimeter of 20 cm.
Does this work for every quadrilateral?
The formulas apply to rectangles and squares. Trapezoids and other quadrilaterals require different area formulas.