Perimeter of a Triangle Calculator

Summary

Enter all three sides to find the perimeter, or enter the perimeter and two sides to find the missing third side.

How it works

1. Choose a calculation mode — "Find Perimeter" or "Find Missing Side".
2. Enter the required values in the input fields.
3. The result updates instantly as you type.
4. Use the Reset button to clear all fields and start over.
5. Copy the result with one click.

Use cases

• Homework and geometry class exercises.
• Architecture and construction measurements.
• Fencing or border planning for triangular plots.
• Game development and 2D geometry calculations.
• Verifying hand calculations quickly.
• Teaching students about the triangle inequality theorem.

Frequently Asked Questions