C# Program to Find Area of Triangle with Example

You can find the area of a triangle in C# by using the formula area = 0.5 * base * height and printing the result, for example: double area = 0.5 * baseLength * height; Console.WriteLine(area);.

Examples

Inputbase = 4, height = 3

OutputArea of triangle is 6

Inputbase = 10, height = 5

OutputArea of triangle is 25

Inputbase = 0, height = 7

OutputArea of triangle is 0

How to Think About It

To find the area of a triangle, you need to know its base length and height. The area is half the product of these two values. So, multiply the base by the height, then divide by 2 to get the area.

Algorithm

1

Get the base length of the triangle from the user

2

Get the height of the triangle from the user

3

Calculate the area using the formula: area = 0.5 * base * height

4

Display the calculated area

Code

csharp

using System;
class Program {
    static void Main() {
        Console.Write("Enter base of triangle: ");
        double baseLength = Convert.ToDouble(Console.ReadLine());
        Console.Write("Enter height of triangle: ");
        double height = Convert.ToDouble(Console.ReadLine());
        double area = 0.5 * baseLength * height;
        Console.WriteLine("Area of triangle is " + area);
    }
}

Output

Enter base of triangle: 4
Enter height of triangle: 3
Area of triangle is 6

Dry Run

Let's trace the example where base = 4 and height = 3 through the code

1

Input base

User enters 4, so baseLength = 4

2

Input height

User enters 3, so height = 3

3

Calculate area

area = 0.5 * 4 * 3 = 6

4

Print result

Output: Area of triangle is 6

Step	Variable	Value
1	baseLength	4
2	height	3
3	area	6

Why This Works

Step 1: Getting inputs

We ask the user to enter the base and height, which are needed to calculate the area.

Step 2: Calculating area

We use the formula area = 0.5 * base * height because the area of a triangle is half the product of its base and height.

Step 3: Displaying output

We print the calculated area so the user can see the result.

Alternative Approaches

Using Heron's formula

csharp

using System;
class Program {
    static void Main() {
        Console.Write("Enter side a: ");
        double a = Convert.ToDouble(Console.ReadLine());
        Console.Write("Enter side b: ");
        double b = Convert.ToDouble(Console.ReadLine());
        Console.Write("Enter side c: ");
        double c = Convert.ToDouble(Console.ReadLine());
        double s = (a + b + c) / 2;
        double area = Math.Sqrt(s * (s - a) * (s - b) * (s - c));
        Console.WriteLine("Area of triangle is " + area);
    }
}

This method calculates area using all three sides, useful when height is unknown but sides are known; it is more complex but versatile.

Using a function to calculate area

csharp

using System;
class Program {
    static double TriangleArea(double b, double h) {
        return 0.5 * b * h;
    }
    static void Main() {
        Console.Write("Enter base: ");
        double baseLength = Convert.ToDouble(Console.ReadLine());
        Console.Write("Enter height: ");
        double height = Convert.ToDouble(Console.ReadLine());
        double area = TriangleArea(baseLength, height);
        Console.WriteLine("Area of triangle is " + area);
    }
}

Using a function improves code reuse and clarity, especially if area calculation is needed multiple times.

Complexity: O(1) time, O(1) space

Time Complexity

The program performs a fixed number of operations (input, multiplication, output), so it runs in constant time.

Space Complexity

Only a few variables are used to store inputs and the result, so space usage is constant.

Which Approach is Fastest?

The direct formula method is fastest and simplest; Heron's formula is slower due to square root calculation but useful when height is unknown.

Approach	Time	Space	Best For
Direct formula (0.5 * base * height)	O(1)	O(1)	Known base and height
Heron's formula	O(1)	O(1)	Known all three sides, height unknown
Function-based calculation	O(1)	O(1)	Code reuse and clarity