How-to

How to Control Equation Numbering in LaTeX

The fix

LaTeX numbers equations automatically inside equation and align. Suppress a number with \nonumber (or \notag) before \\; force a custom label with \tag{...}; group lines as 1a, 1b with the subequations environment (amsmath). Reference an equation with \label and \eqref.

Not sure it worked on your document? Paste it into LetX and compile it, free and in the browser.

Example

\usepackage{amsmath}
\begin{align}
  E &= mc^2 \label{eq:e} \\
  F &= ma \notag
\end{align}
See \eqref{eq:e}.

\begin{subequations}
\begin{align}
  a &= 1 \\
  b &= 2
\end{align}
\end{subequations}

Frequently asked questions

How do I remove the number from one equation?

Put \nonumber (or \notag) before the \\ on that line inside align, or use a starred environment (equation*, align*) to remove all numbers in the block.

How do I reference an equation?

Add \label{eq:key} on the line and cite it with \eqref{eq:key} (from amsmath), which prints the number in parentheses, e.g. (3).

How do I get sub-numbers like (1a) and (1b)?

Wrap the equations in the subequations environment from amsmath; each numbered inner line becomes 1a, 1b, and so on.

Related LaTeX fixes

How-toAlign equationsHow-toAppendixHow-toPage numberingHow-toChemistry (mhchem)

Browse all LaTeX problems & fixes, or start with the LaTeX guide.

Learn the topic properly

Try the fix in LetX

Open the editor, paste your code, and compile in seconds to see the error clear. Free, in your browser.

Open LetX Free