Rectangle Area Calculator
Calculate area, perimeter, and diagonal of a rectangle
📚 Examples, Rules & Help
⚡Quick Examples of Rectangle Area
📐Rectangle Area Formula
Where l = length, w = width. For diagonal: d = √(l² + w²)
🔍How to Calculate Rectangle Area
Understanding Rectangles
A rectangle is a quadrilateral with four right angles (90°). Opposite sides are equal and parallel. It's one of the most fundamental shapes in geometry and everyday life.
Key properties: Length (l), width (w), opposite sides equal, all angles 90°.
Step-by-Step Calculation
Step 1: Identify the length and width of the rectangle
Step 2: For area: multiply length × width
Step 3: For perimeter: add all four sides or use 2(l + w)
Step 4: For diagonal: use Pythagorean theorem √(l² + w²)
Remember: Area is in square units, perimeter and diagonal in linear units.
Why These Formulas Work
Area formula: Area = length × width comes from arranging unit squares. If you have a 4×3 rectangle, you can fit 12 unit squares inside it.
Perimeter formula: P = 2(l + w) adds all four sides. Since opposite sides are equal, we have two lengths and two widths.
Diagonal formula: The diagonal creates a right triangle with the sides, so we use the Pythagorean theorem: d² = l² + w².
🌍Real-World Applications
❓Frequently Asked Questions
What's the difference between a rectangle and a square?
Rectangle: A quadrilateral with four right angles. Length and width can be different.
Square: A special rectangle where all four sides are equal (length = width).
Key point: Every square is a rectangle, but not every rectangle is a square.
How do I find the area if I only know the perimeter and one side?
If you know the perimeter (P) and one side (say length l), you can find the width using:
Formula: w = (P ÷ 2) - l
Then calculate area as usual: A = l × w
What if my measurements are in different units?
How accurate should my measurements be?
Can I use this calculator for irregular rectangles?
🎯Common Use Cases
🏠 Home & Construction
- • Room area calculations for flooring and paint
- • Window and door frame sizing
- • Furniture placement and space planning
- • Garden bed and landscape design
📏 Professional & Technical
- • Technical drawing dimensions
- • Material cutting and waste calculations
- • Display and screen size calculations
- • Packaging and shipping box dimensions
🎨 Creative & Educational
- • Canvas and artwork sizing
- • Photo frame and matting calculations
- • Geometry homework and problem solving
- • Craft project material requirements
🌱 Outdoor & Agriculture
- • Garden plot and raised bed planning
- • Agricultural field area calculations
- • Fence perimeter and material planning
- • Irrigation coverage area calculations