Calculate triangle properties
Our Triangle Calculator is an all-in-one geometric solver that calculates the area, perimeter, semi-perimeter, missing side lengths, and interior angles of any triangle. Supporting multiple input methods—including Base and Height ($A = \frac{1}{2} b h$), Three Sides via Heron's formula ($S = \frac{a+b+c}{2}, A = \sqrt{S(S-a)(S-b)(S-c)}$), and right-angled triangles via the Pythagorean theorem ($a^2 + b^2 = c^2$)—the calculator classifies triangles as equilateral, isosceles, scalene, acute, obtuse, or right-angled while verifying the Triangle Inequality Theorem to guarantee valid geometry.
Multiple calculation modes: Base & Height, Three Sides (SSS), and Right Triangle (hypotenuse)
Implements Heron's formula to solve area accurately from three sides without needing height
Automatic validation of the Triangle Inequality Theorem prevents impossible geometries
Classifies triangle types (equilateral, isosceles, scalene, right) automatically upon entry
Free and private in-browser computation with zero latency and no sign-up barriers
Detailed step-by-step geometric derivations help students learn the underlying math
1. Select your calculation mode: 'Base & Height', 'Three Sides (SSS)', or 'Right Triangle'. 2. Input the known side dimensions or height into the fields. 3. Click 'Calculate Triangle'. 4. Review the computed area, perimeter, semi-perimeter, and geometric triangle classification.
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