How to Indent Nested Lists with Short Labels in enumitem

The indentation of a list is controlled by the space reserved for its label and the gap between that label and the item text. Short labels such as 1. or (a) can make a list look cramped, while nested lists may need different indentation at each level.

The usual fix is to configure each level of the list with enumitem, provide a representative widest label value, and let the package calculate the left margin.

What controls the indentation?

The key settings are:

• label: the label format, such as \arabic*. or (\alph*).
• labelwidth: the space reserved for the label.
• labelsep: the gap between the label and the item text.
• leftmargin: the distance from the surrounding text to the item text.
• widest: a sample value substituted for * when enumitem calculates space for labels.

With leftmargin=*, enumitem calculates a suitable margin using the label width and separation. The label itself can remain short; widest tells the package how much space to reserve. Set these options for each list level because a nested list has its own label format and indentation.

A working example

This complete example uses numbered first-level items and parenthesized lettered subitems. Both levels have their own label-width sample and automatic left margin.

\documentclass{article}
\usepackage{enumitem}

\setlist[enumerate,1]{
  label=\arabic*.,
  widest=99,
  leftmargin=*,
  labelsep=0.6em
}
\setlist[enumerate,2]{
  label=(\alph*),
  widest=m,
  leftmargin=*,
  labelsep=0.6em
}

\begin{document}

\begin{enumerate}
  \item First item, with a nested list.
    \begin{enumerate}
      \item A short subitem label.
      \item Another subitem; its text aligns with the first.
    \end{enumerate}
  \item Second item.
\end{enumerate}

\end{document}

The enumitem package provides the list settings, and \setlist[enumerate,1] and \setlist[enumerate,2] target the first and second levels. The first level reserves space as if its label were 99.; the second uses (m) as its sample. Adjust these samples to match the longest labels your document will use. labelsep=0.6em controls the visible gap, while leftmargin=* derives the overall text indentation from the label dimensions.

If your list may exceed 99 items, choose a wider sample, such as widest=999. The widest value is the content substituted for *; punctuation or parentheses in label are included automatically. You can also put the settings directly in a list, for example \begin{enumerate}[label=\arabic*.,leftmargin=*,widest=99].

When you need exact alignment

If the automatically calculated margin is not the layout you want, use explicit dimensions. For example, leftmargin=2.5em fixes the distance to the item text; choose a value large enough for the label and the desired gap. You can set different fixed values for different nesting levels:

\setlist[enumerate,1]{label=\arabic*.,leftmargin=2.5em}
\setlist[enumerate,2]{label=(\alph*),leftmargin=2em}

A fixed margin is useful when several lists must line up with other page elements. If you set leftmargin explicitly, check that the label has enough room: a long label can extend into the surrounding text if the margin is too small.

For a one-off item with a custom optional label, such as \item[Remark], widest may not account for that label. Either reserve enough space with a larger fixed margin or use a list style intended for descriptive labels. widest is best suited to labels produced by the list’s regular label format.

Common mistakes

• Setting only the first level: Nested lists have separate dimensions. Configure each level whose indentation needs to change.
• Using a sample that is too short: If the actual label is wider than widest, its text may not align with other items. Use a wide enough widest value for the expected number of digits; punctuation in label is included automatically.
• Confusing labelsep with leftmargin: labelsep changes only the gap after the label. It does not by itself set the overall indentation of the item text.
• Expecting leftmargin=* to enforce a fixed page position: It computes a margin from the list’s label dimensions. Use a fixed leftmargin when you need a particular measurement.

Compile the example and adjust widest, labelsep, or the per-level margins to suit the longest labels and the surrounding layout.