Conversion Factors: Mass
While most of us are familiar with converting kilograms or tonnes into pounds and vice versa, mass conversions can become tricky in real-world applications when terms such as tonne, short ton, and long ton are used interchangeably.
The table below captures standard conversions among kilograms, metric tonnes, pounds, short tons, and long tons.
The United States is a large and influential energy market, and energy commentaries can rarely afford not to refer to US market data.
The term “ton” can be ambiguous unless the underlying system—metric, US customary, or imperial—is specified.
In international energy reporting, the metric tonne (1,000 kg) is the global default. In contrast, the short ton (2,000 lb) remains dominant in the United States for reporting statistics such as coal production and consumption.
The :US EIA commonly uses the following abbreviations in its publications:
st → short ton
mst → million short tons
mmst → thousand short tons
The simultaneous use of “m” (million) and “mm” (thousand) reflects legacy US accounting conventions rather than SI-prefix logic, and should therefore be read carefully.
For example, when EIA reports coal production of 600 mst, this refers to 600 million short tons. Since 1 short ton ≈ 0.9072 metric tonnes, this corresponds to approximately 544 million metric tonnes.
Readers comparing US coal data with international sources should always convert short tons into metric tonnes before drawing conclusions.
Differences in mass units also influence how prices are quoted. In the United States, commodity prices are often expressed in cents per pound (¢/lb).
For example, a US ethylene Gulf Coast price may be quoted at 20 cents per pound.
In most other parts of the world, prices are typically expressed in dollars per metric tonne ($/t). Referring to the From / To matrix, 1 metric tonne ≈ 2,205 pounds.
Accordingly, a price of 20 cents per pound translates to:
20 / 100 × 2,205 ≈ $441 per metric tonne.
As a practical rule of thumb, converting from cents per pound to dollars per tonne involves multiplying by approximately 22.
Precious metals such as gold and silver are quoted in troy ounces rather than avoirdupois ounces; this distinction is explained separately in the Gold / Silver prices section.
When different units of volume are introduced alongside mass units, comparisons can become even more complex. The next section addresses precisely that.