Air freight is charging per KG, and Minimum is 45kgs for most of global airports. But Volume will be also taken into account for big volume cargo with small weight.

Interpretation

Weight matters more than Volume

The chargeable unit by Air freight is weight ( per KG ), MIN charge 45KG

For big volume but small weight cargo, then the chargable unit still by KG, but will need to exchange from Volume to Weight . Normally conversion ratio is 1 CBM = 167 kg

For instance

For a 1CBM, 300 KG cargo from Shanghai to Miami,

When the quote is USD 6 / KG, then total Air freight cost is 300 x 6 = USD 1800.

However, if cargo is 2 CBM, 300 KG, then Air freight cost is 2x167 x 6 = USD 2004.