Triangle perimeter
Geometry / FREE CALCULATOR
Add the lengths around a valid triangle.
Your answer starts here.
Enter your values and select Calculate to see the result and any available breakdown.
How to use this calculator
- Enter first side. Use the unit shown beside the field.
- Enter second side. Use the unit shown beside the field.
- Enter third side. Use the unit shown beside the field.
- Select Calculate and review the result. Select Reset to restore the example inputs.
How the calculation works
First side+Second side+Third side
Worked example
First side = 3; Second side = 4; Third side = 5. Result: 12 length units.
Understand your result
Add the lengths around a valid triangle. The result is expressed in length units.
Assumptions and limitations
Each pair of sides must sum to more than the third. Results are rounded for display.
Questions about this tool
What does this tool calculate?
Add the lengths around a valid triangle.
What should I check before using the answer?
Each pair of sides must sum to more than the third.
Related guides
Guides will appear here when published and linked by the editor.