▸A circle with radius 7 cm has circumference 43.9823 cm and area 153.938 cm².
- The diameter (14 cm) is exactly twice the radius and is the longest straight line that fits inside the circle.
- The circumference (43.9823 cm) is roughly 3.141593 times the diameter - that ratio is pi.
- The area (153.938 cm²) grows as the square of the radius, so doubling the radius quadruples the area.
- The area equals C squared divided by (4 pi), confirming the result is self-consistent.
Next stepTo find the area of a sector or the length of an arc, you also need the central angle. Our arc length and sector area calculators cover those.