What is the formula to calculate the circumference of a circle?

The formula to calculate the circumference of a circle is accurately represented as 2π times the radius. This relationship emerges from the fundamental properties of circles, where the radius is the distance from the center of the circle to any point on its perimeter. By multiplying the radius by 2, you effectively obtain the radius's length on both sides of the center, completing a full span across the circle, which is then expressed in terms of π (approximately 3.14) to account for the circle's geometric properties.

In conjunction with this, it's important to note that the diameter of a circle, which is twice the length of the radius, also plays a critical role in determining circumference. The alternative formula that states circumference equals π times diameter relies on this relationship, but it is essentially derived from the initial formula, demonstrating the fundamental link between radius and diameter in circular geometry.

Thus, the option selected presents a direct and conventional formula for circumference, leading to accurate calculations in practical applications such as HVAC systems where circular ducts or components may be involved.