Surface Area of a Rectangle Calculator

Calculate rectangle area, perimeter, and diagonal with step-by-step solutions

Calculate Rectangle Properties

Usually the longer side of the rectangle

Usually the shorter side of the rectangle

Rectangle Formulas

Surface Area: A = ℓ × w

Perimeter: P = 2(ℓ + w)

Diagonal: d = √(ℓ² + w²)

where ℓ = length, w = width

Please enter valid positive values for all required fields

Example Calculations

Example 1: Basic Rectangle

Given: length = 5 m, width = 2 m

Area: 5 × 2 = 10 m²

Perimeter: 2 × (5 + 2) = 14 m

Diagonal: √(5² + 2²) = 5.39 m

Example 2: Monitor Screen

Given: length = 15.6 in, width = 8.8 in

Area: 15.6 × 8.8 = 137.28 in²

Perimeter: 2 × (15.6 + 8.8) = 48.8 in

Diagonal: √(15.6² + 8.8²) = 17.9 in

Quick Reference

Key Formulas

Area = ℓ × w

Perimeter = 2(ℓ + w)

Diagonal = √(ℓ² + w²)

Unit Conversions

1 m = 3.281 ft

1 ft = 12 in

1 m = 100 cm

1 cm = 10 mm

Rectangle Properties

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Four sides: Opposite sides are equal and parallel
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Right angles: All interior angles are 90°
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Diagonals: Equal in length and bisect each other
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2D shape: Has area but no volume

Quick Tips

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Length is usually the longer dimension

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Ensure both dimensions use the same units

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Area is measured in square units (unit²)

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Perimeter is the distance around the edge

Understanding Rectangle Surface Area

What is a Rectangle?

A rectangle is a quadrilateral (four-sided polygon) with four right angles. Opposite sides are equal in length and parallel to each other. Since it's a 2D shape, the term "surface area" is often simply called "area."

The Formula

The surface area formula A = ℓ × w comes from the basic principle that area represents the amount of space inside a shape. For rectangles, this is simply the product of length and width.

Step-by-Step Process

Step 1: Identify Dimensions

Measure or identify the length and width

Step 2: Check Units

Ensure both measurements use the same units

Step 3: Multiply

Calculate A = length × width

Real-World Applications

Construction:

Calculate flooring, roofing, or wall area for material estimation

Technology:

Determine screen area for monitors, tablets, and smartphones

Gardening:

Plan garden beds, calculate seed coverage, or estimate lawn area