Right Triangle Perimeter Calculator
Right Triangle Perimeter Calculator — find perimeter using two legs (Pythagorean theorem) or all three sides.
Formula
c = √(a² + b²); Perimeter = a + b + c
- Pythagorean Theorem: c² = a² + b² (where c is the hypotenuse).
- Perimeter = sum of all three sides: a + b + c.
Legs 3 and 4 units
Inputs
- Leg A (units): 3
- Leg B (units): 4
This is the classic 3-4-5 right triangle. Hypotenuse = 5; Perimeter = 3+4+5 = 12.
Frequently asked questions
What is the Pythagorean theorem?
For a right triangle with legs a and b and hypotenuse c: a² + b² = c². It relates the sides of a right triangle.
What's a 3-4-5 triangle?
A classic right triangle: legs 3 and 4, hypotenuse 5. Check: 3² + 4² = 9 + 16 = 25 = 5² ✓
Do I need to know the hypotenuse?
No, if you have both legs, the calculator finds the hypotenuse using the Pythagorean theorem, then computes perimeter.
Can I use this for non-right triangles?
No, this uses the Pythagorean theorem which only applies to right triangles (with a 90° angle).