Triangle Calculator
Calculate triangle properties: area, perimeter, angles, and sides
Triangle Parameters
Select triangle type and enter known values
Triangle Properties
Calculated triangle measurements and classification
Enter triangle parameters to calculate properties
Famous Triangle Examples
Click to load well-known triangle configurations
3-4-5 Right Triangle
sss
Equilateral Triangle
sss
45-45-90 Triangle
asa
30-60-90 Triangle
asa
Triangle Calculation Methods
Law of Cosines
c² = a² + b² - 2ab·cos(C)
Used when you know two sides and the included angle (SAS) or all three sides (SSS).
Law of Sines
a/sin(A) = b/sin(B) = c/sin(C)
Used when you know two angles and one side (ASA/AAS) or two sides and a non-included angle (SSA).
Heron's Formula
Area = √[s(s-a)(s-b)(s-c)]
Where s is the semiperimeter. Used to calculate area when all three sides are known.
Triangle Inequality
a + b > c, a + c > b, b + c > a
The sum of any two sides must be greater than the third side for a valid triangle.