Circle Calculator

Overview

This circle calculator finds every key measure from a single input. You get radius and diameter plus circumference and area. Choose a unit to label the results for easy reading. Enter one value and the tool calculates all others. It supports reverse work from diameter or circumference or area. Every result shows to four decimal places.

Why Use the Circle Calculator?

Save time and reduce errors on circle math. Start with what you have and finish with a full set of values. Clear units and consistent rounding help you trust the numbers.

• Accurate formulas that use the constant π for all math.
• One field drives all results with a single click.
• Unit selector for millimeters, centimeters, meters, inches, feet, or yards.
• Rounded to four decimals for quick checks and reports.
• Simple controls with Calculate and Clear for fast work.

How It Works

The tool converts your input to a radius, then solves the rest. These formulas guide the process with standard math.

• From diameter: radius equals diameter divided by 2.
• From circumference: radius equals circumference divided by 2π.
• From area: radius equals the square root of area divided by π.

After that it computes these values using the radius.

• Diameter equals 2 times the radius.
• Circumference equals 2π times the radius.
• Area equals π times radius squared.

Choose the unit that matches your input before you calculate. The tool applies that unit to every output. Area uses a squared unit like cm² or m².

Step-by-Step

How to use this circle calculator with confidence. Follow these steps and you are set.

1. Pick a unit from the list or keep No unit.
2. Enter one positive number in only one field.
3. Press Calculate All Properties to get every value.
4. Review the block labeled Complete Circle Properties.
5. Press Clear to reset the fields and results.

What to enter in each field is clear and simple.

• Radius is the distance from the center to the edge.
• Diameter is the distance across the circle through the center.
• Circumference is the length around the edge.
• Area is the space inside the circle.

Use the same unit across your input and output. Positive numbers work best for clean results. Decimals work fine for precise work.

How to read the output is simple and clear.

• Radius, diameter, and circumference use the unit you chose.
• Area shows the squared unit, like in² or ft².
• All values appear with four decimal places for consistency.

Keep these notes in mind for smooth results.

• Use one field at a time, the tool clears the others as you type.
• The unit selector adds labels to your numbers for clarity.
• Pi uses a standard constant for high accuracy.
• Rounding to four decimals may show slight display differences.

Benefits You Can Enjoy

Plan smarter and check work faster with this circle calculator. Students, makers, engineers, and builders all gain from quick math checks. Here are practical ways you can use it today.

• Known radius 5 cm. Diameter 10.0000 cm. Circumference 31.4159 cm. Area 78.5398 cm².
• Known area 50 cm². Radius 3.9894 cm. Diameter 7.9788 cm. Circumference 25.0663 cm.
• Known circumference 31.4159 in. Radius 5.0000 in. Diameter 10.0000 in. Area 78.5398 in².
• Known diameter 0.7 m. Radius 0.3500 m. Circumference 2.1991 m. Area 0.3848 m².

You can check homework, size a round table top, or plan a gasket. You can compute a wheel roll distance or a round post footprint. Clear units and rounded outputs make sharing results simple.

Pick your unit, enter one value, and press Calculate. Clean math, fast results, and zero fuss every time.