Bot version:
!tc temp convtemp (i.e !tc 50 F will say 50 C is 122 F)

on $*:TEXT:/^[!]tc\s+(\d+)\s+(c|f)$/Si:#:{
  if ($regml(2) == C) { msg # $regml(1) F is $round($calc((($regml(1) - 32) / 9) * 5), 2) C }
  else { msg # $regml(1) C is $round($calc((($regml(1) * 9) / 5) + 32), 0) F }
}