# W3cubDocs

/LaTeX

Synopsis:

```\addtolength{len}{amount}
```

Increment the length len by amount. The length name len begins with a backslash, `\`. The `amount` is a rubber length (see Lengths). It can be positive, negative or zero, and can be in any units that LaTeX understands (see Units of length).

Below, if `\parskip` starts with the value `0pt plus 1pt`

```Doctor: how is the boy who swallowed the silver dollar?
then it has the value `1pt plus 1pt` for the second paragraph.
If you did not declare the length len with `\newlength`, if for example you mistype the above as `\addtolength{\specparindent}{0.6\praindent}`, then you get something like ‘Undefined control sequence. <argument> \praindent’. If you leave off the backslash at the start of len, as in `\addtolength{parindent}{1pt}`, then you get something like ‘You can't use `the letter p' after \advance’.