Triangle Calculator
Use this triangle calculator to analyze a general triangle from its three side lengths.
It checks whether the sides form a valid triangle, then reports area, perimeter, semiperimeter, and the three interior angles.
That makes it useful for geometry classes, homework checks, and quick sketches.
The page uses standard U.S.
Assumptions
- The three sides must satisfy the triangle inequality.
- Angles are reported in degrees.
- For right-triangle shortcuts, use the dedicated right triangle calculator.
How this calculator works
Formula used
Area is found with Heron's formula, and angles are found with the law of cosines.
Example calculation
For side lengths 3, 4, and 5, the calculator returns area 6 and angles of about 37, 53, and 90 degrees.
Triangle Calculator FAQ
Is this triangle calculator exact?
It is designed as a practical estimate or classroom calculator for triangle calculator. Results can differ if your teacher, textbook, software, or engineering workflow uses different assumptions, notation, or precision.
Who should use this triangle calculator?
Students, parents, teachers, and everyday users can use it for homework checks, class review, exam prep, and quick planning calculations on a desktop or phone.
Does this replace official coursework, lab software, or professional tools?
No. These pages are educational calculators for learning and general use. For graded work, lab reports, engineering decisions, or research, verify the result with your course method or professional software.