Triangle Calculator
Solve triangle area, perimeter, sides, and angles using SSS, SAS, AAS/ASA, right-triangle, or base-and-height inputs.
Angles are entered in degrees. For AAS/ASA, side a is treated as the side opposite angle A.
Results
Use this Triangle Calculator to calculate triangle sides, angles, perimeter, and area using SSS, SAS, AAS/ASA, right-triangle, or base-and-height information.
Calculation Methods
Perimeter:
P = a + b + c
Base and height area:
A = ½ × base × height
Heron’s formula when all three sides are known:
s = (a + b + c) ÷ 2
A = √[s(s − a)(s − b)(s − c)]
Law of Cosines:
c² = a² + b² − 2ab cos(C)
Law of Sines:
a ÷ sin(A) = b ÷ sin(B) = c ÷ sin(C)
For a right triangle:
a² + b² = c²
Example
For a triangle with sides 5, 6, and 7:
s = (5 + 6 + 7) ÷ 2 = 9
Area = √[9 × 4 × 3 × 2]
Area ≈ 14.70 square units
Important Note
A valid triangle must satisfy the triangle inequality: the sum of any two sides must be greater than the third side. In standard Euclidean geometry, the three interior angles total 180°.
Source
Disclaimer: This Triangle Calculator uses standard Euclidean geometry and trigonometry formulas for educational and general measurement purposes. Results depend on accurate side lengths, angle values, selected units, and the correct solving method. Impossible side combinations, inconsistent angle entries, mixed units, or incorrect included-angle placement can produce invalid results. For construction, engineering, surveying, or safety-critical work, verify all measurements with appropriate professional tools or guidance.