Calculate the area, circumference, and diameter of a circle. Enter either the radius or diameter to get instant results with step-by-step calculations.
Given: Radius = 5 cm
Solution:
A = π × 5² = 25π ≈ 78.54 cm²
C = 2π × 5 ≈ 31.42 cm
d = 2 × 5 = 10 cm
Given: Diameter = 12 in
Solution:
r = 12/2 = 6 in
A = π × 6² = 36π ≈ 113.10 in²
C = 2π × 6 ≈ 37.70 in
Given: C = 31.42 m
Solution:
r = C/(2π) = 31.42/(2π) ≈ 5 m
A = π × 5² ≈ 78.54 m²
d = 10 m
Given: Radius = 1 unit
Solution:
A = π × 1² = π ≈ 3.14159 sq units
C = 2π × 1 = 2π ≈ 6.283 units
Given: Pizza diameter = 16 in
Solution:
r = 8 in, A = π × 64 ≈ 201.06 in²
Pizza area ≈ 201 square inches
A circle is a shape where all points are equidistant from a central point. The distance from the center to any point on the circle is called the radius.
| Property | Formula | Description |
|---|---|---|
| Radius (r) | r | Distance from center to edge |
| Diameter (d) | d = 2r | Distance across circle through center |
| Area (A) | A = πr² | Space inside the circle |
| Circumference (C) | C = 2πr = πd | Distance around the circle |
Pi is a mathematical constant approximately equal to 3.14159. It represents the ratio of a circle's circumference to its diameter and is an irrational number with infinite decimal places.