Triangle Calculator
Right triangle: enter the two short sides (a and b). It finds the hypotenuse, area and perimeter.
What is a triangle calculator?
A triangle calculator works out the missing measurements of a right triangle. Enter the two short sides (a and b) and it finds the hypotenuse, the area and the perimeter, with the working shown step by step.
How to use the triangle calculator
Enter side a and side b, then click Calculate. The calculator shows the hypotenuse c, the area and the perimeter.
Formula
Pythagoras’ theorem: c² = a² + b², so the hypotenuse is c = √(a² + b²). Area = ½ × a × b. Perimeter = a + b + c.
Example
A 3-4-5 triangle: c² = 3² + 4² = 9 + 16 = 25, so c = √25 = 5. Area = ½ × 3 × 4 = 6, and Perimeter = 3 + 4 + 5 = 12.
Frequently Asked Questions
What is the hypotenuse of a 3-4-5 triangle?
The hypotenuse is 5. Try it on the calculator above — set Side a to 3 and Side b to 4.
How do you find the hypotenuse?
Use Pythagoras’ theorem: c = √(a² + b²). For a = 3 and b = 4, c = √(9 + 16) = √25 = 5.
What is the area of a 3-4-5 triangle?
The area is 6: ½ × 3 × 4 = 6.
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