Perimeter of a Triangle Calculator
Calculates the perimeter of a triangle from the measurements you enter. Use any unit, as long as all inputs use the same one.
Result
- Perimeter
- 18
How to use the perimeter of a triangle calculator
- Enter the side a.
- Enter the side b.
- Enter the side c.
- The results update as you type, or press Calculate.
- Read the perimeter first, then the supporting figures below it.
Formula
a + b + c
Worked example
For example, with these inputs:
- Side a: 5
- Side b: 6
- Side c: 7
the calculator returns:
- Perimeter: 18
Background
Each formula has assumptions built in. Area formulas assume flat shapes, volume formulas assume regular solids and statistical measures assume the data you enter is the data you want to describe. Knowing the assumptions helps you pick the right tool.
Calculators are best used to check working rather than replace it, especially for exams where method marks count. Work the problem by hand first, then confirm with the calculator.
Frequently asked questions
How does the perimeter of a triangle calculator work?
It applies this formula: a + b + c
Can I use any units?
Yes, as long as every input uses the same unit. The answer will be in that unit (squared for areas, cubed for volumes).