Despite dimensions may vary slightly, even these numbers should be very close,  the shipping capacity are all theoretical value.

Due to cargo are in different packings, and in different dimensions,  final capacity will differ a lot.

Based on our experience, in most cases, here below the reference CBM for your reference:

26-28 CBM is recommended for 20ft container.

55-58 CBM is recommended for 40ft container.

65-68 CBM is recommened for 40HQ container.