Question 1

What is the difference between radius and diameter?

Accepted Answer

The radius is the distance from the center of the circle to its edge, while the diameter is the distance across the circle passing through the center. Diameter = 2 × radius.

Question 2

Why do we use pi in circle calculations?

Accepted Answer

Pi is a constant ratio between any circle's circumference and its diameter. Its value is approximately 3.14159 and it is an irrational number.

Question 3

How do I calculate the area of a semicircle?

Accepted Answer

Area of semicircle = (pi × r squared) / 2, which is half the area of the full circle.

Question 4

What are the correct units for the results?

Accepted Answer

Radius, diameter, and circumference are in length units (meters, cm), while area is in square units (square meters, square cm).

Question 5

How do I calculate the radius if I know the area?

Accepted Answer

Radius = sqrt(Area / pi). Take the square root of the area divided by pi.

Circle Calculator