Diameter to Circumference Calculator
Convert diameter to circumference instantly with this free calculator. Enter any diameter value and get the circumference, radius, and area of a circle in real time using the formula C = π × d (π ≈ 3.14159). Works for any unit — cm, mm, inches, meters, or feet.
Diameter to Circumference Formula
The formula to convert diameter to circumference is C = π × d. Multiply the diameter by pi (π ≈ 3.14159) and you get the circumference — the total distance around the circle.
Try it — enter a diameter
The diameter is the straight-line distance across the circle through its center. Multiply it by π to get the circumference — the total curved distance around the edge.
Common Diameter to Circumference Conversions
Quick reference table. Formula: C = π × d (π ≈ 3.14159).
| Diameter | Circumference (C = π × d) |
|---|---|
| 1 cm | 3.14 cm |
| 2 cm | 6.28 cm |
| 5 cm | 15.71 cm |
| 10 cm | 31.42 cm |
| 20 cm | 62.83 cm |
| 10 mm | 31.42 mm |
| 25 mm | 78.54 mm |
| 50 mm | 157.08 mm |
| 1 in | 3.14 in |
| 4 in | 12.57 in |
| 10 in | 31.42 in |
| 24 in | 75.40 in |
How to Convert Diameter to Circumference
Converting diameter to circumference takes one step: multiply by π. Here's how to do it.
The Formula
Finding Circumference from Diameter
C = π × d
C — the circumference of the circle
π — pi, approximately 3.14159265
d — the diameter of the circle
💡 Did you know?
Pi (π) is the ratio of circumference to diameter for every circle. That's why C = π × d always works — no matter how large or small the circle is.
Step-by-Step Example
Note the diameter
Example: a pipe has a diameter of d = 5 cm
Multiply by π
Apply C = π × d
Read the result
C = 3.14159 × 5 = 15.708 cm
Going the other way?
d = C ÷ π
Divide circumference by π to get diameter.
Diameter vs Circumference — Interactive
Drag the slider to change the diameter. Watch how the circumference grows proportionally — always π times the diameter.
Diameter
10
Circumference
31.42
Drag to change the diameter