Triangle Calculator
Enter three side lengths to calculate perimeter, area and angles.
How to Use the Triangle Calculator
Enter the known sides or angles requested by the tool to calculate missing triangle values.
Practical Example
A right triangle with legs 3 and 4 has a hypotenuse of 5 and an area of 6 square units.
Factors That Affect the Result
Inputs must describe a valid triangle. Rounding, angle units and incomplete data can affect the result.
Frequently Asked Questions
Can every set of three sides form a triangle?
No. The triangle inequality must be satisfied.
Can the calculator solve right triangles?
Yes, when sufficient values are entered.
Are angles in degrees?
Use the angle unit shown by the tool.
Related Tools
- Pythagorean Theorem Calculator
- Area Calculator
- Distance Formula Calculator
- Slope Calculator
- Midpoint Calculator
Working with Triangle Measurements
A triangle calculator can use known sides or angles to derive missing measurements, but the available formulas depend on the information provided. For a right triangle, the Pythagorean theorem relates the three sides. For general triangles, the law of sines, law of cosines and area formulas may be required. The three interior angles of a Euclidean triangle total 180 degrees, and any two side lengths must add to more than the third side for a valid non-degenerate triangle. Enter all lengths in the same unit and all angles in the unit expected by the calculator. Measurements that are rounded can produce slightly different derived angles or sides, so avoid rounding intermediate values. For construction, surveying or engineering work, account for measurement tolerances and verify critical dimensions with the standards and instruments appropriate to the project.