du -sk ./* | sort -rn | head | \
while read SIZE ENTRY
do
  # if size > 1048576 then it is at least 1 GB big
  if [ ${SIZE} -gt 1048576 ]
  then
    NEWSIZE=$((${SIZE} / 1048576))
    printf "% 10s %s\n" "${NEWSIZE} GB" ${ENTRY#*/}
    # if size > 1024 then it is at least 1 MB big
  elif [ ${SIZE} -gt 1024 ]
  then
    NEWSIZE=$((${SIZE} / 1024))
    printf "% 10s %s\n" "${NEWSIZE} MB" ${ENTRY#*/}
  else
    printf "% 10s %s\n" "${SIZE} KB" ${ENTRY#*/}
  fi
done