Triangle Calculator
Find the area, perimeter, and semi-perimeter of a triangle.
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Introduction
Triangle Calculator — Find the area, perimeter, and semi-perimeter of a triangle. Enter Side a, Side b, Side c to get an instant, accurate result.
Formula
Area via Heron's formula: with semi-perimeter s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)). Perimeter = a+b+c.
Step-by-step
- Enter the Side a.
- Enter the Side b.
- Enter the Side c.
- Click Calculate to see your result instantly.
Real-world example
Example: With Side a = 3, Side b = 4, Side c = 5, the Triangle Calculator gives Area: 6, Perimeter: 12, Semi Perimeter: 6.
Frequently Asked Questions
What if the three sides can't form a triangle?
If the radicand under the square root isn't positive, the sides don't satisfy the triangle inequality and no valid area is returned.
Do I need to know any angles?
No, Heron's formula computes area from the three side lengths alone.
What inputs does the Triangle Calculator need?
You'll need to provide: Side a, Side b, Side c. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Triangle Calculator?
The Triangle Calculator applies the formula exactly as calculated — Area via Heron's formula: with semi-perimeter s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)). Perimeter = a+b+c. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Triangle Calculator free to use?
Yes, the Triangle Calculator is completely free, requires no signup, and runs instantly in your browser.
About the Triangle Calculator
The Triangle Calculator uses a real, verifiable formula — Area via Heron's formula: with semi-perimeter s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)). Perimeter = a+b+c. — so results are accurate every time, not an approximation.