Area of a Rectangle Calculator
Calculate the area, perimeter and diagonal of a rectangle — set the length and width in any unit, and pick a different unit for each result if you like.
About the Area of a Rectangle Calculator
A rectangle's area is the space it covers; its perimeter is the total distance around its edges; its diagonal is the straight line connecting two opposite corners. Length and width each have their own unit selector, and so does every result — pick millimeters for your input and square feet for your area if that's what you need, and the calculator converts everything automatically.
Formulas: Area = a × b · Perimeter = 2(a + b) · Diagonal = √(a² + b²)
A rectangle is a quadrilateral with four right angles, where opposite sides are equal in length and parallel to each other. A square is simply a special case of a rectangle where all four sides happen to be equal. Rectangles show up everywhere in everyday life — screens, doors, tables, rooms, tiles and paper sizes are all rectangular, which is why this is one of the most commonly needed geometry calculations.