Circumference to Diameter Calculator

This circumference to diameter calculator is an essential tool that helps convert the diameter of a circle when given its circumference.

A circular pizza pan with a circumference of 62.8 inches. To find its diameter using our circumference to diameter converter, you would input 62.8 as the circumference. The calculator would then use the formula (explained later) to determine that the diameter is approximately 20 inches.

Circumference to Diameter Calculator

inches Circumference to	Diameter (inches)
1.0 in	0.32 in
1.5 in	0.48 in
2.0 in	0.64 in
2.5 in	0.80 in
3.0 in	0.96 in
3.5 in	1.11 in
4.0 in	1.27 in
4.5 in	1.43 in
5.0 in	1.59 in
5.5 in	1.75 in
6.0 in	1.91 in
6.5 in	2.07 in
7.0 in	2.23 in
7.5 in	2.38 in
8.0 in	2.55 in
8.5 in	2.71 in
9.0 in	2.87 in
9.5 in	3.02 in
10.0 in	3.18 in
10.5 in	3.34 in
11.0 in	3.50 in
11.5 in	3.66 in
12.0 in	3.82 in
12.5 in	3.98 in
13.0 in	4.13 in
13.5 in	4.29 in
14.0 in	4.45 in
14.5 in	4.61 in
15.0 in	4.77 in
15.5 in	4.92 in
16.0 in	5.08 in
16.5 in	5.14 in
17.0 in	5.30 in
17.5 in	5.46 in
18.0 in	5.62 in
18.5 in	5.78 in
19.0 in	5.94 in
19.5 in	6.10 in
20.0 in	6.37 in

Circumference to Diameter Chart

Circumference (units)	Diameter (units)
5	1.59
10	3.18
15	4.77
20	6.37
25	7.96
30	9.55
35	11.14
40	12.74
50	15.92
60	19.10
70	22.00
75	23.87
80	25.46
90	28.65
100	31.83
120	38.20
150	47.74
200	63.66
250	79.25
300	95.49

Circumference to Diameter Formula

The formula to convert circumference to diameter is:

D = C / π

Where:

• D is the diameter
• C is the circumference
• π (pi) is approximately 3.14159

This formula is derived from the well-known equation for the circumference of a circle: C = πD

If a circle has a circumference of 31.4 units: D = 31.4 / π ≈ 10 units

For a circular pool with a circumference of 94.2 feet: D = 94.2 / π ≈ 30 feet

How to Convert Circumference to Diameter?

• Measure the circumference of the circular object accurately.
• Divide the circumference by π (3.14159).
• Round the result to the desired number of decimal places.

For precise calculations, use as many decimal places of π as possible, for most practical applications, using 3.14 is sufficient.

Let’s convert a circumference of 47.1 cm to diameter.

1. Circumference = 47.1 cm
2. 47.1 / π ≈ 14.99 cm
3. Rounded to two decimal places, the diameter is 15.00 cm

What is the Diameter of a 20 Circumference?

The diameter of a circle with a circumference of 20 units is approximately 6.37 units.

To find the diameter of a circle with a circumference of 20 units:

1. Apply the formula: D = C / π
2. Substitute the known values: D = 20 / π
3. Calculate: D ≈ 6.37 units

This result can be verified by calculating the circumference using the found diameter: C = πD = π * 6.37 ≈ 20 units

Is the Circumference 3.14 Times the Diameter?

The circumference is π times the diameter.

While π is often approximated as 3.14, its actual value is an irrational number that continues infinitely without repeating. The first few digits are 3.14159265359…

For everyday calculations, using 3.14 as an approximation for π is usually sufficient. However, in fields requiring high precision, such as aerospace engineering or scientific research, more decimal places of π are used.

Example: For a circle with a diameter of 10 units:

• Approximate circumference: 3.14 * 10 = 31.4 units
• More precise circumference: π * 10 ≈ 31.4159265359 units

The difference is small but can be significant in certain applications.

What is the Diameter of a 21 Inch Circumference?

The diameter of a circle with a 21-inch circumference is approximately 6.68 inches.

To find the diameter of a circle with a 21-inch circumference:

1. Use the formula: D = C / π
2. Substitute the known circumference: D = 21 / π
3. Calculate: D ≈ 6.68 inches

To verify:

1. Calculate the circumference using this diameter: C = πD
2. C = π * 6.68 ≈ 20.99 inches

The slight discrepancy (20.99 vs 21) is due to rounding in our calculations. Using more decimal places in π would yield a more precise answer.

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