You should use something that works with more characters: This is mine ;)

#calc on
on $*:TEXT:/^[!.@]calc|calculate/Si:#: {
  if (!$2) { notice $nick Please use the correct syntax: !calc <calculation> | halt }
  var %output $iif($left($1,1) == @,/msg #,/notice $nick)
  var %scalc $calc($2-)
  var %calc $calc($replace($2-, :, /, x, *))
  %output $2- 4=2 $num(%calc) $iif($short(%scalc),$v1,$chr(32))
  .ignore -u3 $nick
}

alias num { return $bytes($1-,bd) }
alias short {
  if ($1 < 0) { scon 0 return - $!+ $!short( $abs($1) ) }
  if ($1 >= 1000) && ($1 <= 999999) { return 3( $+ $round($calc($1- / 1000),2) $+ k $+ 3) }
  if ($1 >= 1000000) && ($1 < 999999999) { return 3( $+ $round($calc($1- / 1000000),2) $+ m $+ 3) }
  if ($1 >= 1000000000) && ($1 < 999999999999) { return 3( $+ $round($calc($1- / 1000000000),2) $+ b $+ 3) }
  if ($1 >= 1000000000000) && ($1 < 999999999999999) { return 3( $+ $round($calc($1- / 1000000000000),2) $+ t $+ 3) }
}
#calc end