Rectangle Diagonal Calculator
Find the diagonal of any rectangle by entering its length and width. Applies √(l² + w²) for screen sizes, room diagonals, and construction layouts.
Diagonal
Enter values to calculate
How to Use the Diagonal Calculator
1
Enter the rectangle's length.
2
Enter the rectangle's width.
3
Get the diagonal length instantly.
Frequently Asked Questions
How is the diagonal of a rectangle calculated?
Diagonal = √(length² + width²). This is derived from the Pythagorean theorem.
Can I use this for TV or monitor sizes?
Yes — enter the width and height of the display to find the diagonal screen size.
Does it work for squares?
Yes — enter the same value for length and width. The diagonal of a square is s√2.