Triangle Calculator
Solve right triangles — hypotenuse, area, perimeter.
📐 Pythagorean theorem: a² + b² = c². For right triangles only.
What Is This Tool?
This calculator solves right triangles using the Pythagorean theorem. Given the two legs (a and b), it finds the hypotenuse (c), the area, and the perimeter.
The Pythagorean Theorem
For any right triangle, a² + b² = c², where a and b are the legs and c is the hypotenuse (the side opposite the right angle). This is one of the oldest and most useful results in mathematics, proven over 400 different ways.
Common Uses
- Construction: Square corners — measure 3 ft one way, 4 ft the other, diagonal should be 5 ft
- Navigation: Straight-line distance between two GPS points
- TV sizes: A 65-inch TV is measured diagonally
- Ladders: How high a ladder reaches when leaned at an angle
The 3-4-5 Triangle
The simplest Pythagorean triple is 3-4-5: 3² + 4² = 9 + 16 = 25 = 5². Carpenters use it constantly — measure 3 units along one wall, 4 along the other, and adjust until the diagonal is exactly 5. Then the corner is perfectly square.
Frequently Asked Questions
What about non-right triangles?
The Pythagorean theorem only works for right triangles. For other triangles, use the Law of Cosines (c² = a² + b² − 2ab·cos C) or the Law of Sines.
About the Triangle Calculator
The Triangle Calculator lets you figure out triangle 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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