Rectangle Calculator
Get the area, perimeter and diagonal of a rectangle from its width and height.
Rectangle Calculator
Get the area, perimeter and diagonal of a rectangle from its width and height.
How to use the Rectangle Calculator
- Enter the width.
- Enter the height.
- Click Calculate.
Formula
Area = w × h
Perimeter = 2(w + h)
Diagonal = √(w² + h²)
Example
Width 8, height 5: Area = 40. Perimeter = 26. Diagonal ≈ 9.434.
Step-by-step calculation
- Area: 8 × 5 = 40.
- Perimeter: 2 × (8 + 5) = 26.
- Diagonal: √(64+25) = √89 ≈ 9.434.
Real-world uses
- Room and floor measurements.
- Screen and display sizing.
- Card and paper dimensions.
Common mistakes
- Confusing width and height (for rectangles it doesn't matter for area/perimeter, but does for orientation).
- Forgetting to take the square root for the diagonal.
- Using the wrong Pythagorean calculation.
Frequently asked questions
Does it matter which side is width vs height?
No. Area, perimeter, and diagonal are the same regardless of orientation.
What is the diagonal used for?
Useful for checking if a large object fits through a doorway or for screen size measurements.
Can I enter measurements in different units?
Use the same unit for both dimensions. Convert units first if needed.