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Rectangle Area and Perimeter Calculator

Find rectangle area, perimeter, and diagonal from length and width

Rectangle Formula

A = lw, P = 2(l+w), d = √(l²+w²)

Rectangle formulas use the two side lengths. Area multiplies length by width, perimeter adds all four sides, and the diagonal comes from the Pythagorean theorem.

⚠Length and width should be nonnegative. Positive values represent a real rectangle with nonzero area.

How Rectangle Measurements Work

A rectangle has opposite sides equal and four right angles. Its formulas are direct applications of multiplication, addition, and right-triangle geometry.

Area

Space inside equals length times width.

Perimeter

Boundary length adds all four sides.

Diagonal

Corner-to-corner distance uses Pythagorean theorem.

Units

Area uses square units; perimeter uses linear units.

💡 Example: For length 8 and width 5, area=40, perimeter=26, diagonal≈9.434.

Applications of Rectangle Area and Perimeter

Room LayoutsScreensConstructionPackaging

Frequently Asked Questions

What is a rectangle area and perimeter calculator?▼

It calculates area, perimeter, and diagonal from length and width.

What are the rectangle formulas?▼

Area A=lw, perimeter P=2(l+w), and diagonal d=sqrt(l²+w²).

How do I use this calculator?▼

Enter length and width, then click Calculate.

Can length or width be zero?▼

A zero value gives zero area, but a real rectangle usually has positive length and width.

Where are rectangle formulas used?▼

They are used in rooms, screens, fields, construction, and packaging.

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