Circle Circumference Calculator

The circle circumference calculator finds the distance around a circle fast. Enter one value and get clear results. It suits classes, workshops, and quick checks at the bench.

How It Works

The math is simple and standard. Circumference equals 2 times pi times radius. Or circumference equals pi times diameter. Pi is about 3.14159. You can use radius or diameter, then choose your unit. The calculator also reports area, radius, and diameter.

An Easy Process

Here is what each field means and what to enter.

• Input type selects radius or diameter for your entry.
• Value takes a positive number using any decimal you need.
• Unit sets the measurement for all results from the list.

Units include millimeters mm and centimeters cm. Units also include meters m and kilometers km. You can pick inches in and feet ft. You can pick yards yd and miles mi.

Step-by-Step Instructions

1. Pick Input Type and choose radius or diameter.
2. Enter a positive number in the value box.
3. Select a unit from the list shown above.
4. Press Calculate, or press the Enter key.
5. Read the circumference, plus the radius, diameter, and area.

Why Use This Tool?

The circle circumference calculator cuts out hand math and guesswork. It follows the standard formula every time. It supports many units, so you keep work in one system. It also shows area, which helps with material and space plans.

Instant and Reliable

Here is what the outputs mean and how to read them.

• Circumference is the length around the edge of the circle.
• Diameter measures straight across the circle through the center.
• Radius measures from the center point to the edge.
• Area is the space inside the circle shown in square units.

Rounding adapts to your number size for easy reading.

• Circumference under 0.01 shows six decimals.
• Circumference under 0.1 shows four decimals.
• Circumference under 1 shows three decimals.
• All other results show two decimals.

Enter supports quick use, so you can keep your hands on the keyboard. All outputs use the unit you select, so results stay consistent. Area appears in squared form, like cm² or in².

Here are quick examples you can test. Radius 5 cm gives circumference 31.42 cm. Diameter 10 inches gives circumference 31.42 inches. Radius 2 mm gives circumference 12.57 mm. These match the formulas shown above and the rounding rules.