Triangle Calculator
Find all sides, angles, area, and perimeter of any triangle.
How this is calculated
Uses Law of Cosines for SSS/SAS and Law of Sines for ASA. Area = 0.5 x a x b x sin(C).
Frequently Asked Questions About Triangle Calculator
A triangle calculator solves for all sides, angles, area, and perimeter using three different input methods: all three sides (SSS), two sides and an angle (SAS), or two angles and a side (ASA).
What does SSS, SAS, and ASA mean?
SSS = Side-Side-Side (you know all 3 sides). SAS = Side-Angle-Side (you know 2 sides and the included angle between them). ASA = Angle-Side-Angle (you know 2 angles and a side between them). Choose the mode that matches your known values.
How do I calculate triangle area?
Area = 0.5 × base × height. If you know the sides, use Heron's formula or the sine formula: Area = 0.5 × side1 × side2 × sin(included angle). This calculator computes it automatically based on your inputs.
What is the Law of Cosines?
The Law of Cosines states: c² = a² + b² − 2ab×cos(C). It relates the sides and angles of any triangle. It's used to find missing sides when you know two sides and an angle, or to find angles when you know all three sides.
What types of triangles exist?
By sides: equilateral (all equal), isosceles (two equal), scalene (all different). By angles: acute (all angles < 90°), right (one 90° angle), obtuse (one angle > 90°). This calculator identifies the type based on your triangle.
Do the three angles always add up to 180 degrees?
Yes, for any triangle in flat (Euclidean) geometry, the sum of interior angles is always 180°. This is a fundamental property of triangles. If your angles don't sum to 180°, you may have an impossible triangle.
Can I use this for right triangles?
Yes, absolutely. For right triangles with two sides, the third side can be found using the Pythagorean theorem (c² = a² + b²). If you know one angle and one side, you can find the other angle and sides.