Rectangle Calculator
Find the area, perimeter, and diagonal of a rectangle from its two side lengths.
Inputs explained
- Length — The longer side of the rectangle.
- Width — The shorter side of the rectangle.
How to use it
- Fill in the fields above — each input has a hint describing exactly what to enter
- Press Calculate to get your result instantly, right on this page
- Copy the result, save the tool to favorites, or share and embed it anywhere
Understanding the result
Example: A 5 × 4 rectangle has area 20, perimeter 18, and diagonal √41 ≈ 6.4031.
Frequently asked questions
Does a square give a different result than this rectangle calculator? No, a square is just a special case of a rectangle where length equals width, so entering equal values here gives the correct area, perimeter, and diagonal for a square too.
Why is the diagonal longer than either side? The diagonal is the hypotenuse of a right triangle formed by the length and width, so by the Pythagorean theorem it's always longer than either individual side.
Is the Rectangle Calculator free to use? Yes — it is completely free, with no sign-up, no download and no usage limits. You can use it as often as you need.
Is my data private? Yes. The calculation runs entirely in your browser — the values you enter are never sent to our servers, stored or shared with anyone.
What information do I need? Just the following: Length, Width. Each field includes a hint explaining exactly what to enter.
Can I use it on my phone? Yes — the tool is fully responsive and works on any device, and the same calculator is available in the EasyWorkCalcs mobile app.
Privacy
Everything you enter into the Rectangle Calculator is processed entirely in your browser. Nothing is uploaded, stored or shared — your data stays on your device.