Diagonal Length of a Rectangle in Feet Calculator
Calculate the diagonal measurement of any rectangular shape using the Pythagorean theorem
Rectangle Diagonal Calculator
Visual Representation
The diagonal is shown in red
How to Calculate the Diagonal of a Rectangle
The Pythagorean Theorem Formula
The diagonal of a rectangle is calculated using the Pythagorean theorem:
Where:
- d = diagonal length (in feet)
- l = length of the rectangle (in feet)
- w = width of the rectangle (in feet)
Step-by-Step Process
- Measure the length of your rectangle in feet
- Measure the width of your rectangle in feet
- Square both measurements (multiply each by itself)
- Add the squared values together
- Calculate the square root of the sum to find the diagonal length
Example Calculation
For a rectangle with:
- Length = 10 feet
- Width = 6 feet
The diagonal would be:
d = √(10² + 6²) = √(100 + 36) = √136 ≈ 11.66 feet
Practical Applications
Construction & Carpentry
Diagonal measurements are used to ensure rectangles are perfectly square during construction. If both diagonals of a rectangle are equal, the corners are perfect right angles.
Screen & Display Sizes
TV and monitor sizes are measured diagonally. For example, a 55″ TV has a diagonal screen measurement of 55 inches (4.58 feet).
Interior Design
When planning furniture placement, knowing the diagonal of a room or space helps ensure large items can fit through doorways and navigate corners.
Common Rectangle Diagonal Measurements
| Rectangle Dimensions | Diagonal Length | Common Application |
|---|---|---|
| 3 ft × 4 ft | 5 ft | Small tabletop |
| 8 ft × 10 ft | 12.81 ft | Small bedroom |
| 12 ft × 15 ft | 19.21 ft | Living room |
| 16 ft × 9 ft | 18.36 ft | Widescreen TV aspect ratio |
| 24 ft × 36 ft | 43.27 ft | Small warehouse or garage |
Frequently Asked Questions
Why is calculating the diagonal of a rectangle important?
Knowing the diagonal length is crucial for various applications including checking if corners are square in construction, determining TV/monitor sizes, ensuring furniture will fit through doorways, and in mathematics for applying the Pythagorean theorem.
How accurate is this calculator?
This calculator provides results accurate to two decimal places, which is sufficient for most practical applications. For more precision, the full decimal value is calculated internally.
Can I use this calculator for non-rectangular shapes?
No, this calculator is specifically designed for rectangles and squares. For other polygons, different formulas would be required.
What units does this calculator use?
This calculator works with feet as the primary unit of measurement. If you have measurements in other units, you’ll need to convert them to feet before using the calculator.
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