# Size expressions for bordered boxes

Define the outer bounds of a box by using the X-Size and Y-Size properties.

The X-Sizeand Y-Size properties specify the inner size of the box. For example, if a box is 3cm wide and has a 1mm thick border on all sides, the box's outer bounds appear to be 3.2cm wide. This conforms to the CSS specification.

You can define the outer bounds of a box instead:

- Determine the X-Size and Y-Size values by subtracting the width of the borders from the desired height and width. For example, if you want a box to be 3cm wide on the outside while having 1mm borders on all sides, calculate the width to be 3cm-2mm=2.8cm wide.
- If you want a box to have the same size as its parent, set both the
X-Size and Y-Size properties to the value
`max`. You do not have to subtract the borders, since the system automatically adjusts the value of`max`in cases where the box has borders. For example, if the box has a 1mm border and is contained in a box that is 3cm high and wide, the outer bounds of the contained box are also 3cm.

For bordered boxes, do not use expressions
that contain `max` as only one of its components, such as
`max/2`. See following section for details.

## Size expressions that contain the variable max with other components

Expressions such as `max-2cm` or `max/2` can have
unexpected results when you specify the height and width of bordered boxes. Modify these expressions
as follows:

- Take the original formula and replace any occurrence of
`max`with`(max+`, where "`borders`+`padding`+`margin`)`borders`", "`padding`", and "`margin`" denote the width values for each on both sides of the box. - Take the resulting formula (which we'll call "
`f`") from step 1, and create the final formula as.`f`-`borders`-`padding`-`margin`

For example, the original properties box are:

- X-Size =
`max/2` - leftBorderWidth=
`2mm` - leftMargin=
`1mm` - rightBorderWidth=
`1.5mm` - rightPadding=
`3mm`

X-Size is then changed in the following steps:

- X-Size =
`(max+2mm+1mm+1.5mm+3mm)/2`; this is "`f`" in the explanation. - X-Size =
`(max+2mm+1mm+1.5mm+3mm)/2-2mm-1mm-1.5mm-3mm`, which can be consolidated to`(max-7.5mm)/2-7.5mm`.