Triangle Perimeter Calculator
Math
Add the lengths of three valid triangle sides.
Formula
Perimeter = a + b + c
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
Example Calculation
Example inputs
- Side a: 3
- Side b: 4
- Side c: 5
Sides 3, 4 and 5 have a perimeter of 12.
Frequently asked questions
How do I use this calculator?
Enter side a, side b, side c. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Perimeter = a + b + c. Follow the units and definitions shown with the inputs to apply this relationship consistently.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.