Calculate rectangle properties
Our Rectangle Calculator is a 2D Euclidean geometry utility that calculates the area, perimeter, and diagonal length of any rectangular shape. By inputting the length ($l$) and width ($w$) of a rectangle, the tool computes surface area ($A = l \times w$), perimeter ($P = 2(l + w)$), and diagonal corner-to-corner span using the Pythagorean theorem ($d = \sqrt{l^2 + w^2}$). It also functions in reverse, enabling users who know the total area or diagonal alongside one side to deduce the missing dimensions, making it essential for interior designers, carpenters, flooring contractors, and geometry students.
Computes area, perimeter, and diagonal simultaneously with full mathematical precision
Employs the Pythagorean theorem to calculate exact corner-to-corner diagonal distance
Supports reverse calculations: find missing width or length from known area and perimeter
Detects and highlights when entered dimensions form an equilateral square ($l = w$)
Free and private in-browser tool—zero software downloads, ads, or account requirements
Clear, illustrated formula breakdown provides educational transparency for students
1. Enter the length and width of the rectangle in your chosen measurement units. 2. Click 'Calculate'. 3. Inspect the calculated surface area, perimeter distance, and diagonal measurement. 4. Review the step-by-step arithmetic formulas shown below the results.
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