About This Tool
The SSS (Side-Side-Side) case is when you know all three side lengths of a triangle and need to find the angles. This is one of the most common triangle problems โ you can measure three sides of a physical object but angles are harder to measure directly.
This calculator uses the Law of Cosines to find each angle from the three known sides. It also computes the area (using Heron's formula), perimeter, heights, inradius, circumradius, and shows a scaled diagram of your triangle.
Enter your three side lengths below and get the complete solution instantly. The calculator automatically validates that your sides can form a valid triangle (the sum of any two sides must be greater than the third).
How to Use
1. Enter the length of side a (opposite to angle A)
2. Enter the length of side b (opposite to angle B)
3. Enter the length of side c (opposite to angle C)
4. All angles and properties are calculated instantly
5. View the step-by-step solution showing how each angle was found
6. Toggle between degrees and radians for angle display
7. Copy the shareable link to save your calculation
Formula
Law of Cosines (to find angles from sides):
cos(A) = (bยฒ + cยฒ - aยฒ) / (2bc)
cos(B) = (aยฒ + cยฒ - bยฒ) / (2ac)
cos(C) = (aยฒ + bยฒ - cยฒ) / (2ab)
Area (Heron's Formula):
s = (a + b + c) / 2
Area = โ[s(s-a)(s-b)(s-c)]
Triangle Inequality:
a + b > c, a + c > b, b + c > a