Diameter Symbol (⌀)

Copy, Type & Learn About the Diameter Symbol

⌀

What is the Diameter Symbol?

⌀

The Standard Diameter Symbol

The standard diameter symbol consists of a perfect circle with a 45° line that extends outside the circle. This is the officially recognized symbol for indicating diameter measurements in technical and mathematical contexts.

Technical Details:

  • Unicode Name: "Diameter Sign"
  • Unicode: U+2300
  • Decimal Code: 8960
  • HTML Entity: ⌀
  • LaTeX: \diameter

Alternative Names:

  • Diameter sign
  • Phi symbol (common misconception)
  • Circle with stroke
  • Diameter notation

Similar Symbols and Differences:

Symbol Name Difference
⌀ Diameter Symbol Official diameter symbol with a perfect circle and 45° line extending outside
Ø Scandinavian Letter O with Stroke Often used as an alternative, but technically a different character (Unicode 00D8)
∅ Empty Set Mathematical symbol for empty set (Unicode 2205)
⊘ Circled Division Slash Mathematical operation symbol (Unicode 2298)

How to Type the Diameter Symbol

Windows Alt Code Method

To type the diameter symbol using Alt code:

Alt + 8960 → ⌀

Note: This only works with the numeric keypad. For laptops without a numeric keypad, use alternative methods below.

Windows

Unicode Method
Type 2300 then Alt + X
Emoji Picker
Windows + .
Character Map

Search for "Diameter Sign"

Mac

Keyboard Shortcut
⇧ Shift + ⌥ Option + O
Character Viewer
Control + Command + Space

Search for "Diameter Sign"

Microsoft Office

Word Excel PowerPoint

  1. Click Insert → Symbol
  2. Search for "diameter"
  3. Double-click the symbol

Google Workspace

  1. Insert → Special Characters
  2. Search for "diameter" or "o"
  3. Click to insert the symbol

Tips & Notes

  • Windows Alt code only works with the numeric keypad
  • For laptops without a numeric keypad, use the Character Map or emoji picker
  • On Mac, the Character Viewer can be enabled in System Preferences
  • Most modern text editors support Unicode input

Common Uses of the Diameter Symbol

Proper Usage Guidelines

Correct Format

  • ✓ ⌀50mm
  • ✓ ⌀ 100cm
  • ✓ Pipe ⌀75
  • ✓ ⌀25.4±0.1mm
  • ✓ Hole ⌀6.35

Incorrect Format

  • ✗ 50mm⌀
  • ✗ diameter50mm
  • ✗ D=50mm
  • ✗ DIA 50mm
  • ✗ Ø50mm

Engineering & Technical

  • Technical drawings and blueprints
  • CAD software documentation
  • Engineering specifications
  • Mechanical part dimensions
  • CNC machining instructions

Examples:

  • ⌀50mm bearing
  • Hole ⌀10±0.1mm
  • Thread ⌀M8×1.25

Manufacturing

  • Pipe and tube specifications
  • Construction materials
  • Industrial equipment
  • Quality control documents
  • Assembly instructions

Examples:

  • PVC pipe ⌀100mm
  • Steel rod ⌀12mm
  • Wire ⌀0.8mm

Mathematics

  • Geometric calculations
  • Mathematical proofs
  • Educational materials
  • Scientific papers
  • Problem-solving guides

Examples:

  • Circle ⌀5 units
  • Area = π(⌀/2)²
  • ⌀r = 2x

Digital Design

  • Technical illustrations
  • User interface elements
  • Icon design
  • Design specifications
  • Infographics

Examples:

  • Button ⌀40px
  • Avatar ⌀56px
  • Logo size ⌀100px

Important Notes

  • Always place the ⌀ symbol before the measurement value
  • Include appropriate units after the number
  • Use proper precision for technical measurements
  • For tolerances, use format: ⌀50±0.1mm

Frequently Asked Questions

General Questions

Why can't I find the diameter symbol on my keyboard?

The diameter symbol (⌀) is a special character that isn't included on standard keyboards. This is because it's primarily used in technical and scientific contexts. Instead, you'll need to use keyboard shortcuts, character codes, or the system's character map to insert it.

Is Ø the same as the diameter symbol ⌀?

No, although they look similar and are sometimes used interchangeably, they are different characters. ⌀ (U+2300) is the official diameter symbol, while Ø (U+00D8) is actually a Scandinavian letter. The proper diameter symbol ⌀ has a perfect circle with a 45° line extending outside.

Why does the diameter symbol look different in some fonts?

Font rendering of the diameter symbol can vary depending on the font family and system support. Some fonts might display it as Ø or ∅ if they don't include the proper diameter symbol. For technical documents, it's recommended to use fonts that correctly support the U+2300 character.

Alt Code Questions

What is the Alt Code for the diameter symbol?

The Alt Code for the diameter symbol is Alt + 8960. To use it:

  1. Hold down the Alt key
  2. Type 8960 on your numeric keypad
  3. Release the Alt key
  4. The diameter symbol ⌀ will appear

Why isn't the Alt Code working?

Common reasons why Alt Codes might not work:

  • You're not using the numeric keypad (the numbers above the letter keys won't work)
  • Num Lock isn't enabled on your keyboard
  • You're using a laptop without a numeric keypad
  • Your system's language settings don't support the character

What if my keyboard doesn't have a numeric keypad?

If you don't have a numeric keypad, you can use these alternatives:

  • Use the Character Map (Windows) or Character Viewer (Mac)
  • Use the Unicode method (type 2300 then Alt+X)
  • Copy and paste the symbol from a website or document
  • Use the Windows emoji picker (Windows key + .)

Technical Usage

Should I put the diameter symbol before or after the measurement?

The diameter symbol (⌀) should always be placed BEFORE the measurement value. For example: ⌀50mm is correct, while 50mm⌀ is incorrect. This is the standard convention in technical drawing and engineering.

How do I write diameter with tolerances?

When specifying tolerances, place them after the measurement value. For example: ⌀50±0.1mm. For bilateral tolerances, use: ⌀50+0.1/-0.05mm. The diameter symbol should always come first.

Can I use the diameter symbol in CAD software?

Yes, most modern CAD software supports the diameter symbol. You can typically insert it using keyboard shortcuts or through the software's dimension tools. Some CAD programs automatically convert "DIA" or "D" to the proper symbol ⌀ in dimension annotations.

Software & Compatibility

Why doesn't the diameter symbol work in my email/document?

This usually happens when the font being used doesn't support the diameter symbol or when the character encoding isn't properly set. Try using a different font (like Arial or Times New Roman) or ensure your document is using UTF-8 encoding.

Will the diameter symbol display correctly on all devices?

Most modern devices and operating systems support the diameter symbol. However, some older systems or devices with limited font support might display it as a rectangle or placeholder character. For maximum compatibility, you can include a fallback notation (e.g., "dia." or "D") in critical documents.

How do I use the diameter symbol in programming/HTML?

In HTML, you can use the decimal entity ⌀ or the hexadecimal entity ⌀. In programming, you can use the Unicode escape sequence \u2300. Make sure your files are encoded in UTF-8 to properly support the symbol.

Common Issues & Solutions

Symbol appears as a box or question mark

  • Try changing to a different font
  • Ensure your system's language settings support Unicode
  • Update your operating system or browser
  • Check if the document encoding is set to UTF-8

Keyboard shortcuts not working

  • Make sure you're using the numeric keypad for Alt codes
  • Check if Num Lock is enabled
  • Try using the character map/symbol picker instead
  • Verify your keyboard layout settings

Symbol not copying/pasting correctly

  • Copy the symbol from a Unicode-compatible source
  • Use a plain text editor first to verify the symbol
  • Check if the destination application supports Unicode
  • Try using the symbol's HTML entity code instead

Font compatibility issues

  • Use common fonts like Arial or Times New Roman
  • Test the symbol in your target font before using
  • Consider using a technical font for documentation
  • Keep a list of compatible fonts for reference