Triangle calculator
Solved in your browser. Nothing is uploaded.
Result
- a
- 3
- b
- 4
- c
- 5
- A
- 36.8699°
- B
- 53.1301°
- C
- 90°
- Area
- 6
- Perimeter
- 12
- Height to a
- 4
- Height to b
- 3
- Height to c
- 2.4
- Inscribed circle radius
- 1
- Circumscribed circle radius
- 2.5
- Type
- scalene, right
Working
- Right triangle: Pythagoras and sine/cosine give the rest.
- a² + b² = c² → 3² + 4² = 5²
- sin A = a / c → A = 36.8699°
- B = 90° − A = 53.1301°
- Area = ½ · b · c · sin A = 6
How to use this tool
Solve any triangle from three values, or a right triangle from two. Nothing is uploaded.
Open Triangle calculator
Tick Right triangle if C is 90°. Side a is opposite angle A, and so on.
Enter what you know
Type three values (two for a right triangle), at least one of them a side.
Read the result
Every side, angle, area, perimeter and height appears with a drawing and the working. Copy result copies it.
FAQ
How do I solve a triangle?
Enter three values, at least one of them a side: three sides (SSS), two sides and the angle between them (SAS), two angles and a side (ASA or AAS), or two sides and another angle (SSA). For a right triangle, two values are enough.
How are the sides and angles labelled?
Side a is opposite angle A, b opposite B and c opposite C. In a right triangle C is the right angle, so c is the hypotenuse.
Why are there two answers?
Two sides and an angle that is not between them (SSA) can fit two different triangles, one with an acute angle and one with an obtuse angle. The calculator shows both.
How is the area found?
Area = ½ × b × c × sin A, which gives the same result as Heron's formula. For a right triangle that is ½ × a × b.
What units does it use?
Angles are in degrees. Sides can be in any unit, as long as all of them use the same one; the area is in that unit squared.