calcy treasure chest of featuresLove the calculators but not the ads?

Take a sneak peek at the Ad-Free Design being enjoyed by hundreds of members for less than 25¢ a week. Full details and a bonus!

Circle Calculator to Calculate Area, Circumference, Diameter, Radius

Calculator Preferences
Circle Calculator Sign
Circle Calculator

This calculator will solve for the three unknown circle measurements from one known measurement (area, circumference, diameter, or radius). Plus, the calculator displays the steps, formulas, and sequence used to calculate each unknown measurement in the results. The Learn tab includes a circle diagram depicting each measurement, accompanied by a brief definition of each and the method of solving for them.

Learn More

Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Convert Ft/In to DecimalConvert Feet/Inches to DecimalConvert Feet/Inches to DecimalConvert Feet/Inches to Decimal

Enter the feet, inches, and fraction of an inch, and then click the Convert to Decimal button. You can then copy the appropriate decimal and paste into the circle calculator.

Feet:
Inches:
-/
Feet:
Inches:

Convert Feet/Inches to Decimal:

If you need to convert a tape measurement into a decimal number, tap the button in this row to expand the converter.

Dec places:Decimal places:Number of decimal places:Number of decimal places to round result to:

Number of decimal places:

Select how many decimal places you would like the result rounded to. Note that you can change the number of places before or after calculating the circle measurement. Also note that the circle calculator will always display the raw results (out to 14 places) in the steps that will appear beneath the calculator.

Area (A):

Select the known value and just start typing.

Circle Area Calculator
A =

Mini Circle Area Calculator:

Select the known circle measurement from the drop-down menu and then enter the selected measurement in decimal format. The circle's area (A) will be calculated as you type. Click the Clear button to clear both fields.

Area (A):

If you know the area of the circle and would like to calculate the circumference, diameter, and radius, enter the area on this line. Enter only digits 0-9 and a decimal point (if applicable). Non-numeric characters will not compute.

Or, tap the plus (+) to expand the mini calculator if you need to find the area.

Note that the area of a circle is expressed as the square of the particular unit of measurement being used (square mm, square inches, etc.).

 
Circumference (C):
Circumference Calculator
C =

Mini Circumference Calculator:

Select the known circle measurement from the drop-down menu and then enter the selected measurement in decimal format. The circle's circumference (C) will be calculated as you type. Click the Clear button to clear both fields.

Circumference (C):

If you know the circumference of the circle and would like to calculate the area, diameter, and radius, enter the circumference on this line. Enter only digits 0-9 and a decimal point (if applicable). Non-numeric characters will not compute.

Or, tap the plus (+) to expand the mini calculator if you need to find the circumference.

 
Diameter (D):

Select the known value and just start typing.

Diameter Calculator
D =

Mini Diameter Calculator:

Select the known circle measurement from the drop-down menu and then enter the selected measurement in decimal format. The circle's diameter (D) will be calculated as you type. Click the Clear button to clear both fields.

Diameter (D):

If you know the diameter of the circle and would like to calculate the area, circumference, and radius, enter the diameter in the field on this line. Enter only digits 0-9 and a decimal point (if applicable). Non-numeric characters will not compute.

Or, tap the plus (+) to expand the mini calculator if you need to find the diameter.

 
Radius (r):

Select the known value and just start typing.

Radius Calculator
d =

Mini Radius Calculator:

Select the known circle measurement from the drop-down menu and then enter the selected measurement in decimal format. The circle's radius (r) will be calculated as you type. Click the Clear button to clear both fields.

Radius (r):

If you know the radius of the circle and would like to calculate the area, circumference, and diameter, enter the radius in the field on this line. Enter only digits 0-9 and a decimal point (if applicable). Non-numeric characters will not compute.

Or, tap the plus (+) to expand the mini calculator if you need to find the radius.

 

If you would like to save the current entries to the secure database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

Convert Decimal to Ft/InConvert Decimal to Feet/InchesConvert Decimal to Feet/InchesConvert Decimal to Feet/Inches

Enter the decimal number, tap Feet or Inches, select the maximum denominator, and then click the Convert to Feet/Inches button. The converter will round the fraction portion to the selected denominator and then reduce it to simplest form.

Decimal:
Type:
Max Denom:Max Denom:Max Denominator:Maximum Denominator:
Feet:
Inches:
-/

Convert Feet/Inches to Decimal:

If you need to convert a decimal to a tape measurement, copy a decimal from the above results and tap the button to expand the converter.

Decimal number:

Enter the decimal number you would like to convert into a tape measurement.

Feedback AppreciatedFeedback Greatly AppreciatedYour Feedback Would Be Greatly AppreciatedYour Feedback Is Greatly Appreciated
Heading

Tip

About

About the Circle Calculator

This geometry calculator will take one known circle measurement (area, circumference, diameter, or radius) and calculate the other three.

Plus, unlike other online circle calculators, this calculator will show its work and give a detailed, step-by-step explanation of the formulas and sequence used to arrive at each result.

For your convenience, the calculator also includes 4 mini calculators you can access by tapping the plus (+) icon on each circle measurement line ...

  • Circle Area Calculator
  • Circumference Calculator
  • Diameter Calculator
  • Radius Calculator

... and 2 conversion calculators for converting between tape measurements (feet/inches) and decimal numbers (one button appears at the top of the calculator and the other appears at the bottom).

If you are unfamiliar with the common measurements used in plane circle geometry, it may help to visit the Learn tab to learn about them before using the calculator.

Discover the benefits of subscribing to the Ad-Free Member Version of my website.
Learn how I went from being trapped in a work I hated to being free to work at what I love.

Instructions

How to use the Circle Calculator

Step #1:

Select the number of decimals places you would like the calculated measurements rounded to.

Step #2:

Enter the known circle measurement into its corresponding field, and make sure the other three measurement fields are empty.

Step #3:

Tap the "Calculate Circle" button. This will calculate the values for the unknown measurements, plus display the formulas and steps the calculator used to solve for them.

Saving Entries:

If your web browser supports Local Storage, you can save your entries to your web browser so won't have to start over on your next visit. Please note that your saved entries can only be retrieved from the same device and web browser you were using when you stored them. If you would like to access your saved entries from any device I invite you to subscribe to the Ad-Free Member Version.

To save your entries to your web browser, click or tap the Data tab in the Help and Tools section (mobile: top right of the main screen), select "New Data Record" from the drop-down menu, enter a name for the data record, and then tap or click the Save button.

To load previously saved entries, click or tap the Data tab and select the saved data record from the drop-down menu. You can then save any changes to your entries by simply clicking the Save button while the data record is selected.

To clear a named set of saved entries, click or tap the Data tab, select the saved data record from the drop-down menu, and then tap or click the Clear button.

Numbers and Decimals:

Only numeric characters (0-9 and decimal points) may be entered in numeric fields. Non-numeric characters (dollar signs, percent signs, commas, etc.) may cause calculation errors. If the field includes a grid icon, tapping the icon will open a popup keypad which will include only the characters allowed in the field. If your device keypad does not include a decimal point, use this popup keypad to enter decimal numbers where applicable.

Popup Tool Tips:

Tap the info (i) icons for a further explanation of each entry field (you can click [X] or outside of the pop-up tool tips to close them). A summary of these explanations, along with any additional term explanations, can also be found under the Terms tab.

Disclaimer:

Since I can't test for every possible combination of numbers, please be sure to double-check the results of this calculator yourself before considering them to be valid. If you do discover an issue with the calculated results, please report the issue using the feedback form located below the calculator.

Scrolling & Shrinking:

In order to scroll the calculator vertically you will need to swipe just outside of the calculator's dark-blue border, or use the window's far right-hand scroll bar, whichever is applicable to your device.

If the top section of the calculator becomes to tall for your viewport, tapping in the "Enter a problem..." field should reset the top section to its original height.

Disclaimer:

The Algebra Calculator is the only calculator on the site that I did not create myself. And since I did not create it, I don't have access to the code for fixing any issues you may be experiencing. So if you are having issues with the calculator, please visit the support page at Mathway.com for assistance.

Glossary

Fields, Terms, and Definitions.

Reset button:

Clicking the "Reset" button will restore the calculator to its default settings.

Pocket Calculator

Calculate any amounts needed to enter into calculator.

 

Data Management

Save and retrieve entries and notes (requires HTML5 compliant web browser).

Calculator Data

Calculator Data:

If you are using the latest version of your web browser software, this feature will allow you to save your calculator entries to your web browser's local storage in between visits. This means the calculator entries can only be recalled with the same device and web browser you were using when you saved them. If you'd like to save data between devices you will need to subscribe to the Ad-Free Member Version.

Save: To save a new set of calculator entries, select "New Data Record" from the dropdown list, enter a nickname for the data record, then click the "Save" button.

Load: To load a previously saved set of calculator entries, simply select the name of the data record from the dropdown list.

Save Changes: To save changes to a set of previously saved calculator entries, be sure the name of the data record is selected, and then click the "Save" button.

Clear: To clear a saved set of entries, be sure the name of the data record is selected, and then click the "Clear" button.

Backup Data
My Notes:
Subscribe to the Cloud level of the Ad-Free Member Version to save your entries and notes to a secure online database, allowing you to access your saved entries from any device or web browser.

Sorry! The Save functions are bonus features reserved for those who allow ads to display on the page.

If you would like to use the Save features, please disable ad blocking for this website and refresh the page. Or you can choose to subscribe to the Ad-Free Member Version of the site.

Help and Tools

Help and Tools:

This section, which you can Unstick or Hide in the Calculator Preferences (just above the top of the calculator), contains the following tabs (content too long to fit within bordered frame can be scrolled up and down):

About: Click this tab for an introduction to the calculator.

Instructions: Click this tab for step-by-step instructions for using the calculator.

Terms: Click this tab for a list of the descriptions that are located within each popup help button (info icons).

PCalc: Click this tab for a handy "pocket" calculator you can use when you need to calculate an entry needed for the calculator.

Data: Click this tab to save a set of entries or a note in between visits. Entries and notes will be stored to your web browser's local storage (if supported by your browser of choice), meaning they can only be recalled with the same device and web browser you were using when you saved them. If you'd like to save entries and notes between devices you can do so by subscribing to the Ad-Free Member Version.

 

Favorites

Add or remove this page to/from my favorites.