Rectangle Calculator
Find rectangle area, perimeter, and diagonal.
▭ Area = width × height. Diagonal uses the Pythagorean theorem.
What Is This Tool?
This calculator finds the area, perimeter, and diagonal of a rectangle from its width and height. One of the most practical calculations in daily life.
The Formulas
- Area = width × height
- Perimeter = 2 × (width + height)
- Diagonal = √(width² + height²)
Everyday Uses
- Flooring: How much tile or carpet to buy
- Paint: Wall area for paint estimation
- Screens: TV and monitor sizing (diagonal)
- Land: Lot and property dimensions
- Fabric: Material for curtains, tablecloths
Square Footage
In the US, area is often measured in square feet. For a 12 × 15 foot room: 12 × 15 = 180 sq ft. To convert to square meters, multiply by 0.0929 (180 sq ft ≈ 16.7 m²).
Frequently Asked Questions
How much extra flooring should I buy?
Add 10% for waste and cutting mistakes. For patterned materials that need matching, add 15-20%. Order slightly more than you think you need — dye lots vary between batches.
About the Rectangle Calculator
The Rectangle Calculator lets you figure out rectangle calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
How to Use This Tool
- Enter the main values the calculator asks for (for example, amount, rate, and time).
- Pick the right unit or option where the tool offers a choice.
- Read the result, which appears instantly below the inputs.
- Adjust any field to test a different scenario — the answer updates without a reload.
- Copy or note the result. Nothing is stored, so close the tab when you're done.
Why Use an Online Calculator?
Browser-based tools like this one have a few real advantages over installed software or manual methods:
- No installation. It opens instantly in any browser, on any operating system.
- Private by default. Everything runs locally, so your data stays on your device.
- Always up to date.There's nothing to update — you always get the latest version when you load the page.
- Free and unlimited. Use it as often as you like, with no account and no caps.
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