Rectangle Calculator
Fill in the values and the answer updates as you type.
How the Rectangle Calculator works
Area = length × width. Perimeter = 2 × (length + width).
Inputs and results
The Rectangle Calculator takes 2 inputs and gives 3 results.
What you enter
- Length — starts at 8.
- Width — starts at 5.
What you get
- Area
- Perimeter
- Diagonal
Example: Rectangle Calculator with the starting values
With length 8 and width 5, the calculator returns:
| Area | 40 |
|---|---|
| Perimeter | 26 |
| Diagonal | 9.434 |
Change any value above and the results update straight away.
Rectangle Calculator FAQ
How do I use the Rectangle Calculator?
Enter length and width in the fields, then read area, perimeter and diagonal in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Rectangle Calculator calculate?
Area, perimeter, and diagonal of a rectangle. It returns area, perimeter and diagonal from the 2 values you provide.
What values does the Rectangle Calculator start with?
It opens with length 8 and width 5 so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Rectangle Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Rectangle Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.