Rectangle Area Calculator

Calculate the area, perimeter, and diagonal of a rectangle. Enter the length and width to get instant results with step-by-step calculations and visual diagrams.

length (l) width (w) diagonal (d)

Rectangle Formulas:

Area: A = l × w
Perimeter: P = 2(l + w)
Diagonal: d = √(l² + w²)

Special Case: Square

A square is a rectangle with equal sides. Enter the side length to calculate its properties.

side (s)
Square Formulas: A = s², P = 4s, d = s√2

Examples

Example 1: Basic Rectangle

Given: Length = 10 cm, Width = 5 cm

Solution:

A = 10 × 5 = 50 cm²

P = 2(10 + 5) = 30 cm

d = √(100 + 25) = √125 ≈ 11.18 cm

Example 2: Room Dimensions

Given: Room 12 ft × 10 ft

Solution:

A = 12 × 10 = 120 ft²

P = 2(12 + 10) = 44 ft

Flooring needed: 120 sq ft

Example 3: Square

Given: Side = 8 m

Solution:

A = 8² = 64 m²

P = 4 × 8 = 32 m

d = 8√2 ≈ 11.31 m

Example 4: Picture Frame

Given: Frame 16 in × 12 in

Solution:

A = 16 × 12 = 192 in²

P = 2(16 + 12) = 56 in

Diagonal ≈ 20 in

Example 5: Golden Rectangle

Given: Length = 16.18, Width = 10

Solution:

A = 161.8 units²

Ratio (phi) ≈ 1.618

Classic golden ratio proportions

About Rectangle Calculations

What is a Rectangle?

A rectangle is a four-sided polygon with four right angles (90 degrees). Opposite sides are parallel and equal in length. A square is a special type of rectangle where all sides are equal.

Rectangle Properties

Property Formula Description
Area A = l × w Space enclosed by the rectangle
Perimeter P = 2(l + w) Distance around the rectangle
Diagonal d = √(l² + w²) Distance between opposite corners

Special Formulas for Squares

When length equals width (a square), the formulas simplify to:

  • Area: A = s² (side squared)
  • Perimeter: P = 4s (four times side)
  • Diagonal: d = s√2 (side times square root of 2)

Practical Applications

  • Flooring and carpet calculations
  • Wall painting and wallpaper coverage
  • Land and property measurement
  • Construction and architecture
  • Screen and display dimensions