How to Type the Sigma Symbol (σ Σ) on a Keyboard

Two versions with different uses — here’s every method on every platform

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The sigma symbol comes in two forms that serve different purposes, and knowing which one you need matters before looking up the method.

Both are Greek letters with distinct mathematical meanings, and both have reliable methods on every platform.

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The Two Sigma Symbols

σ — lowercase sigma (Unicode U+03C3). Used in statistics for standard deviation, in physics for various constants, and in mathematics generally. The most commonly needed version in scientific and academic writing.

Σ — uppercase Sigma (Unicode U+03A3). Used in mathematics as the summation operator — the notation for adding a series of values. Also appears in physics and engineering.

Both are covered in the methods below.

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Windows

Method 1: Alt Codes

For lowercase σ: hold Alt and type 229 on the numeric keypad.

For uppercase Σ: hold Alt and type 228 on the numeric keypad.

• Num Lock must be on
• Use the numeric keypad only — not the number row
• Doesn’t work on laptops without a dedicated numpad

Method 2: Character Map

Search for Character Map in the Start menu. Find σ or Σ in the Greek character block, copy, and paste. Works on any Windows machine regardless of numpad availability.

Method 3: System-Wide Text Expansion

Use PhraseExpress, AutoHotkey, or Espanso to map triggers to both symbols system-wide. Works across every application.

A simple AutoHotkey script covering both:

::\sigma::σ
::\Sigma::Σ

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Mac

Method 1: Keyboard Shortcut

Press Option + W to type the lowercase σ instantly.

For uppercase Σ, press Option + W gives σ on most Mac keyboard configurations. For Σ specifically, press Option + Shift + W or use the Character Viewer to confirm the exact shortcut for your keyboard layout.

Note: Mac keyboard shortcuts for Greek letters vary slightly by region and keyboard layout. If Option + W doesn’t produce σ on your specific configuration, use the Character Viewer to find the correct shortcut for your setup.

Method 2: Character Viewer

Press Control + Command + Space to open the Character Viewer. Search “sigma” and double-click σ or Σ to insert. This works regardless of keyboard layout and is the most reliable method on Mac.

Method 3: Greek Keyboard Layout

Go to System Settings → Keyboard → Input Sources and add the Greek keyboard. With Greek active, σ is on the S key and Σ is on Shift + S. Switch between keyboards using the input menu in the menu bar.

Method 4: Text Replacement

Go to System Settings → Keyboard → Text Replacements and map triggers like \sigma to σ and \Sigma to Σ. Works system-wide across every Mac app.

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iPhone and iPad

Method 1: Greek Keyboard

Go to Settings → General → Keyboard → Keyboards → Add New Keyboard and add Greek. With Greek active, tap S for σ and Shift + S for Σ. Switch keyboards using the globe icon.

This is the most practical method for regular sigma use on iOS — the Greek keyboard puts both symbols exactly where you’d expect them.

Method 2: Text Replacement

Go to Settings → General → Keyboard → Text Replacement. Add σ as the phrase with \sigma as the shortcut, and Σ with \Sigma as its shortcut. Auto-expands in any app after setup.

Method 3: Long Press on S Key

Some iOS keyboards show Greek variants on long press of Latin letters. Try holding the S key and see if σ appears in the popup. This varies by iOS version and keyboard configuration.

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Android

Method 1: Add Greek Keyboard

In Gboard settings, go to Languages → Add Keyboard and add Greek. With Greek active, S produces σ and Shift + S produces Σ. Switch between keyboards using the globe icon or language switcher.

Method 2: Gboard Symbol Search

In Gboard, tap the G logo and use the search function. Type “sigma” and both σ and Σ appear as insertable options.

Method 3: Long Press on S Key

On some Android keyboards, long pressing the S key reveals σ as an extended character option. Try holding S and checking the popup.

Method 4: Text Replacement

In Gboard settings, go to Dictionary → Personal Dictionary, select your language, and add σ with shortcut \sigma and Σ with shortcut \Sigma.

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Chromebook

Method 1: Unicode Input

For lowercase σ: press Ctrl + Shift + U, type 03c3, then press Enter or Space.

For uppercase Σ: press Ctrl + Shift + U, type 03a3, then press Enter or Space.

Method 2: Add Greek Input Method

Go to Settings → Device → Keyboard → Input Methods and add Greek. With Greek active, σ is on S and Σ is on Shift + S.

Method 3: Special Characters Picker

Press Search + Shift + Space to open the emoji and special characters panel. Search “sigma” and select σ or Σ.

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Linux

Method 1: Unicode Input

For lowercase σ: press Ctrl + Shift + U, type 03c3, then press Enter.

For uppercase Σ: press Ctrl + Shift + U, type 03a3, then press Enter.

Works consistently across most Linux distributions.

Method 2: Compose Key

With a Compose key configured, Greek letters are accessible through compose sequences on some distributions. Check your specific compose key table for sigma sequences.

Method 3: Greek Keyboard Layout

Add the Greek keyboard layout through your input method settings. On the Greek layout, σ is on the S key and Σ is on Shift + S — the most intuitive and fastest method for regular use.

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Microsoft Word (Any Platform)

Method 1: Alt + X

For σ: type 03C3 then immediately press Alt + X.

For Σ: type 03A3 then immediately press Alt + X.

Word converts the Unicode code point to the symbol instantly.

Method 2: Insert Symbol With AutoCorrect

Go to Insert → Symbol → More Symbols. Select Greek and Coptic from the character set dropdown. Find σ or Σ, click Insert, then click AutoCorrect to set triggers like \sigma and \Sigma that Word converts automatically.

Method 3: Equation Editor

For mathematical documents where sigma appears in formal equations, press Alt + = to open an equation field and type \sigma or \Sigma followed by Space. Word’s equation editor renders properly formatted math-mode sigma symbols.

This is the right approach for summation notation — the equation editor handles the full Σ notation including subscripts and superscripts correctly.

Method 4: Alt Codes

For σ: hold Alt and type 229 on the numpad. For Σ: hold Alt and type 228 on the numpad.

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Google Docs

Character Viewer on Mac (Control + Command + Space) works inside Google Docs. The Alt codes work on Windows inside Docs.

For equations, go to Insert → Equation and type \sigma or \Sigma followed by Space — Google’s equation editor renders them correctly in math formatting, including the full summation notation with limits.

Go to Insert → Special Characters, search “sigma,” and click to insert for occasional inline use.

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LaTeX

In LaTeX, both sigma symbols are typed as commands in math mode:

latex

% Standard deviation example
The standard deviation is $\sigma = 2.4$.

% Summation notation
$\Sigma_{i=1}^{n} x_i$

% Or using the sum environment for better formatting
$\sum_{i=1}^{n} x_i$

Note that LaTeX has a dedicated \sum command that produces a properly sized summation operator — better formatted than \Sigma for actual summation notation in display math. Use \Sigma when you need the literal Greek letter and \sum when you’re writing a summation.

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HTML and Web Development

html

<!-- Lowercase sigma -->
&sigma;       <!-- named entity -->
&#963;        <!-- decimal -->
&#x03C3;      <!-- hex -->
σ             <!-- direct character -->

<!-- Uppercase Sigma -->
&Sigma;       <!-- named entity -->
&#931;        <!-- decimal -->
&#x03A3;      <!-- hex -->
Σ             <!-- direct character -->

Named entities σ and Σ are the most readable options in HTML source code.

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Quick Reference Table

Symbol	Platform	Fastest Method	Shortcut
σ	Windows	Alt code (numpad)	Alt + 229
Σ	Windows	Alt code (numpad)	Alt + 228
σ	Mac	Character Viewer or Greek keyboard	Control + Command + Space
Σ	Mac	Character Viewer or Greek keyboard	Control + Command + Space
σ / Σ	iPhone / iPad	Greek keyboard	Add Greek, tap S / Shift + S
σ / Σ	Android	Gboard search or Greek keyboard	Search “sigma” in G menu
σ	Chromebook	Unicode input	Ctrl + Shift + U, 03c3
Σ	Chromebook	Unicode input	Ctrl + Shift + U, 03a3
σ	Linux	Unicode input	Ctrl + Shift + U, 03c3
Σ	Linux	Unicode input	Ctrl + Shift + U, 03a3
σ	Microsoft Word	Code conversion	Type 03C3 then Alt + X
Σ	Microsoft Word	Code conversion	Type 03A3 then Alt + X
σ / Σ	LaTeX	Math commands	\sigma / \Sigma in math mode

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The Bottom Line

Adding the Greek keyboard is the best long-term solution on any platform if you use sigma and other Greek letters regularly — it puts σ on the S key and Σ on Shift + S, which is the most intuitive mapping available and requires no memorization of codes or shortcuts.

For occasional use, the Character Viewer on Mac and Gboard’s symbol search on Android find both symbols in seconds without any setup. On Windows, Alt + 229 and Alt + 228 cover both versions reliably with a numpad.

For mathematical documents in Word, LaTeX, or Google Docs, the equation editor approach using \sigma and \Sigma produces properly formatted math-mode output — important when sigma appears in equations with subscripts, superscripts, or as part of formal summation notation.

For Greek letters in general, adding the Greek keyboard is the one setup that makes every Greek character instantly accessible — σ on S, Σ on Shift + S, and the rest of the alphabet exactly where you’d expect it.