How it works
Fill in the 2 fields above and Rectangle Diagonal Calculator calculates the result instantly, recalculating as you change any value. It applies the formula d = √(l² + w²). The math runs locally in your browser — nothing is sent to a server.
Formula
d = √(l² + w²)Examples
- Length 16, Width 9 → Diagonal: 18.3576
Frequently asked questions
How do I use the Rectangle Diagonal Calculator?
Enter your values in the 2 input fields and the result is calculated automatically as you type. Change any value to see the numbers update instantly.
What formula does the Rectangle Diagonal Calculator use?
It uses d = √(l² + w²). The calculation is performed in your browser using standard, well-established math for accurate results.
Is my data private?
Yes. The Rectangle Diagonal Calculator runs entirely in your browser. Nothing you enter is uploaded, saved to a server, or shared — it never leaves your device.
Is the Rectangle Diagonal Calculator free?
Yes, it is completely free with no sign-up, no limits and no watermarks. Like every tool on math and the rest of the platform, you can use it as often as you like.
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