Greek letters · U+3A3

ΣSigma symbol

Σ is the Sigma character. It is text, not a picture — it takes the colour of the type around it and pastes into anything.

How to type it
Unicode
U+3A3
Alt code
Alt+931
HTML
Σ
Unicode name
Greek Capital Letter Sigma
Σ
Your font
01 — Origin

Where the Sigma symbol comes from

Capital sigma as the summation sign is Euler’s, introduced in 1755 — sigma for the Latin summa. Before that, sums were written out in words or with dots, and there was no way to state the limits of a sum compactly.

Summation in maths and statistics, standard deviation in its lowercase form, and the sigma of six-sigma manufacturing. In spreadsheets the same letter labels the autosum button.

Worth knowing
Σ and σ are not interchangeable: the capital sums a series, the lowercase names a standard deviation. Using one where the other belongs reverses the meaning of the formula.
02 — Codes

Sigma symbol codes

Tap any value to copy it. All of them produce the same character — they just belong to different places.

03 — How to type

How to type Σ on any keyboard

Keyboard, code, markup or document — the route to U+3A3 differs by tool.

Windows
Hold Alt and type 931 on the numeric keypad, then release. Without a keypad, use the Character Map app (search “charmap”).
Mac
Press Control + Command + Space to open the character viewer, then search “sigma”. Double-click to insert.
Phone
There is no shortcut on a phone keyboard. Tap the symbol at the top of this page, then long-press in any text field and choose Paste.
Web and code
In HTML write Σ or Σ. In CSS content: "\03A3". Make sure the page is served as UTF-8 and the raw character works too.
04 — Font support

Will Σ actually show up?

We checked 147 fonts installed on a normal machine and counted how many of them contain this character. A symbol missing from a font is drawn as an empty box — the text is still correct, it just cannot be drawn.

86% 127 of 147 fonts

Safe in most places. Common fonts have it. Older or decorative fonts sometimes do not, so a fallback font will kick in.

05 — Similar

Symbols people confuse with Σ

Lookalikes that are not the same character at all — separate codes, separate fonts, and here they number 8.

06 — Related

Other Greek letters used as symbols

The rest of the family, one page each — origin, typing routes and font support, across all 5.

Ω Omega symbolIn 86% of system fonts α Alpha symbolIn 86% of system fonts β Beta symbolIn 86% of system fonts Δ Delta symbolIn 86% of system fonts λ Lambda symbolIn 86% of system fonts
07 — Same block

Greek letters

Alpha to omega, the alphabet science borrowed.

All greek letters →
08 — FAQ

Sigma symbol — questions

How do I type the Sigma symbol?
On Windows hold Alt and type 931 on the numeric keypad. On Mac open the character viewer with Control + Command + Space and search “Sigma”. Or just tap the symbol on this page — it goes straight to your clipboard.
What is the HTML code for Σ?
Write it as Σ or Σ in HTML, \03A3 in CSS content, and \u03A3 in JavaScript. All four produce the same character.
Is Σ an emoji?
No. Σ is a text character — it takes the colour of the text around it and works in usernames, filenames and documents. An emoji is replaced by a colour picture and is sometimes stripped by forms and systems.
Why does Σ show as a box on some devices?
Because that font has no drawing for this character. We checked 147 fonts on a normal machine and 127 of them include it. The character itself is always correct; only the drawing is missing.