What is an avoirdupois ounce?
An avoirdupois ounce is the ordinary ounce of the imperial and US customary systems, as opposed to the troy ounce used for gold and silver.
It is equal to 1/16 of a pound or approximately 28.35 grams. The avoirdupois system is based on a pound of 16 ounces, with larger units such as tons and pounds used for heavier measurements.
What is a long hundredweight?
A long hundredweight, also known as the imperial hundredweight, is the hundredweight of the United Kingdom and, despite the name, is not 100 pounds. The 100 pound version is the short hundredweight used in the United States.
It is equivalent to 112 pounds or approximately 50.802 kilograms. The long hundredweight is often used in trade and commerce for measuring bulk goods such as grains, coal, and other commodities.
To get metric tons, multiply long hundredweights by 0.0508, since one is about 50.802 kilograms and a metric ton is 1,000 – 5 long hundredweights is about 0.254 metric tons. Dividing by 20 gives long tons instead, because 20 hundredweights make a long ton.