Diagonal of Rectangle Table: Diagonal by Length
Reference table of diagonal for Diagonal of Rectangle across a range of length values — exact, engine-computed figures you can read off at a glance.
Diagonal of Rectangle Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Diagonal
5.0000
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Diagonal of Rectangle Calculator
The Diagonal of Rectangle Calculator works out your diagonal in an instant. Enter length and width and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the length.
- Enter the width.
- Read off your diagonal — the calculator updates automatically, with no button to press.
Formula
The Diagonal of Rectangle Calculator uses the formula:
Diagonal = √(Length ^ 2 + Width ^ 2)
Worked example
For example, with length of 3 and width of 4, the diagonal is 5.0000.
| Length | 3 |
|---|---|
| Width | 4 |
| Diagonal | 5.0000 |
|---|
Results are estimates for educational use, not professional advice.
Frequently asked questions
Use the Pythagorean theorem: the diagonal is the square root of (length² + width²). A 3 by 4 rectangle has a diagonal of 5.
The diagonal splits the rectangle into two right triangles, with the length and width as the two legs.
Yes. Screen sizes are measured diagonally, so this finds the diagonal from the panel's width and height.
The same units as the sides you enter, such as centimetres, inches or metres.
The Diagonal of Rectangle Calculator uses the formula: Diagonal = √(Length ^ 2 + Width ^ 2). For example, with length of 3 and width of 4, the diagonal is 5.0000.
Enter the length. Enter the width. Read off your diagonal — the calculator updates automatically, with no button to press.
Related guides
How to Calculate Diagonal of Rectangle: Formula, Steps & Examples
Learn how to calculate Diagonal of Rectangle — the formula explained step by step, with worked examples and a free calculator to check your answer.