Zend certified PHP/Magento developer

How to output disk size in GB only with no rounding error? [duplicate]

Output disk size in GB only. Giga Bytes only.
Not MB. Not Mega Bytes.
Not TB. Not Tera Bytes.

Tested thus far:

sudo blockdev --getsize64 /dev/sda
1000204886016

sudo blockdev --getsize64 /dev/sda |bc -l |awk '{print $1/1000000000}'
1000.2

sudo blockdev --getsize64 /dev/sda |bc -l |awk '{print $1/1000000000}' |numfmt --field=1- --format=%.0f --invalid=ignore
1001

But above 1001 output is a rounding error.
1000 is ideal output, meaning 1000 GB disk size.

Question1:
How to fix above rounding error?

Question2:
What is a more elegant way or shorter way versus 120 characters below:
sudo blockdev --getsize64 /dev/sda |bc -l |awk '{print $1/1000000000}' |numfmt --field=1- --format=%.0f --invalid=ignore

.
.

using:
neofetch --stdout |grep 'OS:'

OS: Kubuntu 22.04.3 LTS x86_64