### 4.1.2 Paper size and automatic scaling

#### Setting the paper size

‘A4’ is the default value when no explicit paper size is set. However, there are two functions that can be used to change it:

`set-default-paper-size`
```#(set-default-paper-size "quarto")
```

which must always be placed at the toplevel scope, and

`set-paper-size`
```\paper {
#(set-paper-size "tabloid")
}
```

which must always be placed in a `\paper` block.

If the `set-default-paper-size` function is used in the toplevel scope, it must come before any `\paper` block. `set-default-paper-size` sets the paper size for all pages, whereas `set-paper-size` only sets the paper size for the pages that the `\paper` block applies to. For example, if the `\paper` block is at the top of the file, then it applies the paper size to all pages. If the `\paper` block is inside a `\book`, then the paper size applies only to that book.

When the `set-paper-size` function is used, it must be placed before any other functions used within the same `\paper` block. See Automatic scaling to paper size.

Paper sizes are defined in file ‘scm/paper.scm’; see section Predefined paper sizes for a complete list.

Both `set-default-paper-size` and `set-paper-size` also accept a quoted number pair as its argument to set a custom paper size.

```#(set-default-paper-size '(cons (* 100 mm) (* 50 mm)))
```

The units `in` (inches), `cm` (centimeters), `mm` (millimeters), and `pt` (points) can all be used.

If the symbol `'landscape` is added to the paper size function as a second argument, pages are rotated by 90 degrees, and wider line widths are set accordingly.

```#(set-default-paper-size "a6" 'landscape)
```

Swapping the paper dimensions without having the print rotated (like when printing to postcard size, or creating graphics for inclusion rather than a standalone document) can be achieved by appending ‘landscape’ to the name of the paper size itself:

```#(set-default-paper-size "a6landscape")
```

When the paper size ends with an explicit ‘landscape’ or ‘portrait’, the presence of a `'landscape` symbol only affects print orientation, not the paper dimensions used for layout.

Notation Reference: Automatic scaling to paper size, Predefined paper sizes.

Installed Files: ‘scm/paper.scm’.

#### Automatic scaling to paper size

If the paper size is changed with one of the scheme functions (`set-default-paper-size` or `set-paper-size`), the values of several `\paper` variables are automatically scaled to the new size. To bypass the automatic scaling for a particular variable, set the variable after setting the paper size. Note that the automatic scaling is not triggered by setting the `paper-height` or `paper-width` variables, even though `paper-width` can influence other values (this is separate from scaling and is discussed below). The `set-default-paper-size` and `set-paper-size` functions are described in Setting the paper size.

The vertical dimensions affected by automatic scaling are `top-margin` and `bottom-margin` (see Fixed vertical spacing `\paper` variables). The horizontal dimensions affected by automatic scaling are `left-margin`, `right-margin`, `inner-margin`, `outer-margin`, `binding-offset`, `indent`, and `short-indent` (see Horizontal spacing `\paper` variables).

The default values for these dimensions are set in ‘ly/paper-defaults-init.ly’, using internal variables named `top-margin-default`, `bottom-margin-default`, etc. These are the values that result at the default paper size `a4`. For reference, with `a4` paper the `paper-height` is `297\mm` and the `paper-width` is `210\mm`.