Sigma in LaTeX

The LaTeX command for sigma (σ) is \sigma. The capital form Σ is \Sigma.

\sigma

Greek Lowercase · Unicode σ (U+03C3) · no package needed

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Which command should you use?

Command	Package	Use it when
`\sigma` recommended	none	Standard deviation, stress, singular values.
`\Sigma`	none	Capital: covariance matrix.
`\sum`	none	Summation sign: larger, with proper limits.
`\varsigma`	none	Final-form sigma.

Table 1. Ways to write sigma in LaTeX. Every line was compiled with pdfLaTeX (TeX Live 2026) loading only the package shown.

Common mistake. Write sums with \sum, not \Sigma: \sum is sized for display math and places limits above and below.

How to type Sigma

Write \sigma inside math mode, that is between $…$ for inline math or in a \[ … \] or equation block for display math. It is part of core LaTeX math, so no extra package is required.

Example

$\sum_{i=1}^{n} (x_i - \mu)^2 = n \sigma^2$

\sum_{i=1}^{n} (x_i - \mu)^2 = n \sigma^2

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Related Greek Lowercase symbols

\mu\nu\xi\pi\varpi\rho\varrho\varsigma\tau\upsilon\phi\varphi\chi\psi

Lowercase Greek letters in LaTeX: the full table or search all 350+ LaTeX symbols.

FAQ

How do you write sigma (σ) in LaTeX?

Use \sigma in math mode; it needs no extra package. For example, $\sum_{i=1}^{n} (x_i - \mu)^2 = n \sigma^2$.

Which package provides \sigma?

None: \sigma is built into LaTeX, so no extra package is required.

What is the most common mistake with sigma in LaTeX?

Write sums with \sum, not \Sigma: \sum is sized for display math and places limits above and below.