Find Missing Side of a Triangle Calculator
Published On: 05/03/2026
Find Missing Side of a Triangle Calculator
Find a missing triangle side using either the Pythagorean theorem (right triangles) or the Law of Cosines (any triangle with two sides and the included angle).
Right triangle inputs:
• Choose what you want to solve for: hypotenuse or a leg.
• Enter the two known sides. The calculator uses: c² = a² + b².
• Choose what you want to solve for: hypotenuse or a leg.
• Enter the two known sides. The calculator uses: c² = a² + b².
Find Missing Side of a Triangle — Description
The Find Missing Side of a Triangle Calculator helps you solve for an unknown side length using two common methods. For right triangles, it uses the Pythagorean theorem (c² = a² + b²) to find the hypotenuse or a missing leg. For non-right triangles, it uses the Law of Cosines (c² = a² + b² − 2ab cos(C)) when you know two sides and the included angle. Enter your known values, choose the method, and the calculator returns the missing side instantly.