Math can be applied directly to variable values.
Example 3.7. math examples
{$foo+1}
{$foo*$bar}
{* some more complicated examples *}
{$foo->bar-$bar[1]*$baz->foo->bar()-3*7}
{if ($foo+$bar.test%$baz*134232+10+$b+10)}
{$foo|truncate:"`$fooTruncCount/$barTruncFactor-1`"}
{assign var="foo" value="`$foo+$bar`"}
Although Smarty can handle some very complex expressions and syntax, it is a good rule of thumb to keep the template syntax minimal and focused on presentation. If you find your template syntax getting too complex, it may be a good idea to move the bits that do not deal explicitly with presentation to PHP by way of plugins or modifiers.