Circumference of a Circle in Feet Calculator
Calculate the circumference, area, diameter, or radius of any circle with precision
Diameter: 0 feet
Circumference: 0 feet
Area: 0 square feet
Circle Visualization
Circle Formulas
Circumference Formula
The circumference of a circle is the distance around it.
C = 2πr
C = πd
Where:
- C = Circumference
- r = Radius
- d = Diameter
- π (pi) = 3.14159…
Area Formula
The area of a circle is the space contained within its circumference.
A = πr²
A = πd²/4
Where:
- A = Area
- r = Radius
- d = Diameter
- π (pi) = 3.14159…
Radius Formula
The radius is the distance from the center to any point on the circumference.
r = C / 2π
r = √(A / π)
r = d / 2
Diameter Formula
The diameter is twice the radius and represents the longest distance across the circle.
d = 2r
d = C / π
d = 2 × √(A / π)
Example Calculations
Example 1: Finding the Circumference of a Circle
For a circle with a radius of 5 feet:
Circumference = 2 × π × r
Circumference = 2 × 3.14159 × 5
Circumference = 31.4159 feet
Example 2: Finding the Area of a Circle
For a circle with a diameter of 10 feet:
First, find the radius: r = d/2 = 10/2 = 5 feet
Area = π × r²
Area = 3.14159 × 5²
Area = 3.14159 × 25
Area = 78.5398 square feet
Example 3: Finding the Diameter from Circumference
For a circle with a circumference of 40 feet:
Diameter = C / π
Diameter = 40 / 3.14159
Diameter = 12.7324 feet
Circle Measurement Conversion Table
| Radius (ft) | Diameter (ft) | Circumference (ft) | Area (sq ft) |
|---|---|---|---|
| 1 | 2 | 6.28 | 3.14 |
| 2 | 4 | 12.57 | 12.57 |
| 3 | 6 | 18.85 | 28.27 |
| 4 | 8 | 25.13 | 50.27 |
| 5 | 10 | 31.42 | 78.54 |
| 6 | 12 | 37.70 | 113.10 |
| 7 | 14 | 43.98 | 153.94 |
| 8 | 16 | 50.27 | 201.06 |
| 9 | 18 | 56.55 | 254.47 |
| 10 | 20 | 62.83 | 314.16 |
Practical Applications
Construction
Calculating circular foundations, pools, pillars, and other structures requires accurate circumference measurements.
Landscaping
Designing circular gardens, patios, or determining fencing requirements for round areas.
Engineering
Designing pipes, wheels, cylindrical tanks, and other circular components.
Frequently Asked Questions
What is the formula for calculating the circumference of a circle?
The formula is C = 2πr (where r is the radius) or C = πd (where d is the diameter).
What is the relationship between diameter and radius?
The diameter is twice the radius: d = 2r.
How do I find the radius if I know the circumference?
Divide the circumference by 2π: r = C / 2π.
How accurate is the value of π used in calculations?
This calculator uses JavaScript’s built-in Math.PI constant, which provides π to approximately 15 decimal places, sufficient for most practical applications.
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