Rectangle Area Calculator
Area, perimeter and diagonal.
Enter your values
Enter the length you are working with.
Enter the width you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Area
- 90
- Perimeter
- 39
- Diagonal
- 14.15097
- Aspect ratio
- 1.6
- Is it a square?
- No
Quick answer
A rectangle's area is length times width; the diagonal follows from Pythagoras.
A = l × w
At a glance
| What it does | Area, perimeter and diagonal. |
|---|---|
| Category | Math |
| Inputs needed | Length, Width |
| Main output | Area |
| Formula | A = l × w |
| Cost | Free — no sign-up, no download |
How to use the Rectangle Area Calculator
- 1Enter the length.
- 2Enter the width in the same unit.
- 3Read area, perimeter and diagonal.
Inputs explained
- Length
- Enter the length you are working with.
- Width
- Enter the width you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Length12
- Width7.5
Results
- Area90
- Perimeter39
- Diagonal14.15097
- Aspect ratio1.6
- Is it a square?No
Frequently asked questions
What unit is the area?
Whatever you entered, squared — enter feet and you get square feet.
How do I find area from perimeter?
You cannot without another dimension; many rectangles share a perimeter.
What do I need to enter into the Rectangle Area Calculator?
Just 2 values: length, width. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Rectangle Area Calculator work out the answer?
A rectangle's area is length times width; the diagonal follows from Pythagoras. It applies the formula A = l × w and shows the working so you can check each step by hand.
Is the Rectangle Area Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.