OMNI Tonnage is recorded in Net Ton, also known as Short Ton. A unit of weight equal to 2,000 pounds (0.907 metric ton or 907.18 kilograms).

Long Ton, also known as Gross Ton: A unit of weight equal to 2,240 pounds (1.016 metric tons or 1,016.05 kilograms).

Metric ton: A unit of weight equal to 2,204.6 pounds (1000 kilograms).

A unit of capacity for cargo in maritime shipping, normally estimated at 40 cubic feet.

Gross Register Ton: A unit of internal capacity of a ship equal to 100 cubic feet.

A unit for measuring the displacement of ships, equal to 35 cubic feet, and supposed to equal the volume taken by a long ton of seawater.

Long/Gross Tons * 1.12 = Net/Short Tons

Metric Tons * 1.1023 = Net/Short Tons

Wikipedia Conversion of Units: http://en.wikipedia.org/wiki/Conversion_of_units