How can I know the exact void ratio of rainwater harvesting module?

Void ratio determines a rainwater harvesting module can load how much water, then how to calculate the void ratio? Check below examples, hope it will help.

Given: p = m/v , p= 0.92g per cubic centimeter, m is weight, V is volume.

Take 1 CBM M2016S tank as example 1

Each M2016S tank is 9.42kg, total 4pcs tank per CBM (1CBM=1000000 cubic centimeter)

m=9.42X4=37.68kg, V= 37.68/0.92≈40.96, 40.96/1000000≈0.00004

The void ratio of each M2016S is 96%.

Take 1 CBM M2015F tank as example 2 (When installation, 2pcs tank only use 1 big plate, so during the calculation we need take out excess spare plate)

Each M2015F tank is 11.97kg, total 5pcs tank per CBM

m=11.97X5=59.85kg, 59.85-6.68(4pcs spare plate)=53.17kg,

V=53.17/0.92≈57.79, 57.79/1000000≈0.00005

The void ratio of each M2015F is 95%.

Below is our Rainwater Harvesting tanks NEWEST void ratio: