Phi in LaTeX

The LaTeX command for phi (ϕ) is \phi. The capital form Φ is \Phi.

\phi

Greek Lowercase · Unicode ϕ (U+03D5) · no package needed

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Which command should you use?

Command	Package	Use it when
`\phi` recommended	none	Straight-stroke phi: the golden ratio, a phase.
`\varphi`	none	Loopy phi: angles, Euler's totient, test functions.
`\Phi`	none	Capital: the normal CDF, magnetic flux.
`\emptyset`	none	The empty set, which is not a phi.

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

Common mistake. \phi is a Greek letter, not the empty set: write \emptyset, or \varnothing (amssymb) for the round form.

How to type Phi

Write \phi 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

$\phi = \frac{1 + \sqrt{5}}{2}$

\phi = \frac{1 + \sqrt{5}}{2}

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Often confused with

Varphi \varphi (φ): variant phi (script)
Emptyset \emptyset (∅): empty set
Varnothing \varnothing (∅): variant empty set (preferred)

Related Greek Lowercase symbols

\varpi\rho\varrho\sigma\varsigma\tau\upsilon\varphi\chi\psi\omega\alpha\beta\gamma

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

FAQ

How do you write phi (ϕ) in LaTeX?

Use \phi in math mode; it needs no extra package. For example, $\phi = \frac{1 + \sqrt{5}}{2}$.

Which package provides \phi?

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

What is the most common mistake with phi in LaTeX?

\phi is a Greek letter, not the empty set: write \emptyset, or \varnothing (amssymb) for the round form.