awk - To take only the number in Size in unix -

i trying identify file contributing more in directory structure. doing following steps manually

example: du -sh * [0-9]g give me folders inside having gb size.

2.0g images 3.7g files 8.9g audio 

i want variable take highest sized directory size 8.9, how can in awk or grep

i might change bit to:

du -sk .??* * | sort -rn | head -1 

the interesting difference .??* * catch pesky "hidden" directories. chief among offenders .cache.