Tonnes vs. Tons: Metric vs. Imperial Measurements Strike Again

A tonne, also called a metric ton or metric tonne, is a metric unit of mass equal to 1,000 kilograms (about 2,204 pounds).

The word "tonne" comes from French and the metric system, which most countries use for measuring weight and distance. During the 20th century, the metric system (including the tonne) became the standard for science, engineering, and international commerce.

The word "ton" belongs to the Imperial system and U.S. customary system. In Imperial measurement you will encounter two common kinds:

When a document says “ton,” context matters. U.S. trade reports usually mean the short ton, while older U.K. sources often mean the British long ton.

NIST’s Handbook 44 explains these definitions in its Units and Systems of Measurement appendices, and the UK’s Weights and Measures Act 1985 banned the use of the Imperial ton for trade, effectively mandating the metric tonne.

To compare quickly: 1 tonne is essentially 1.102 short tons or 0.984 long tons.

The majority of countries use the tonne because the metric system is standard in international trade. Canada measures export commodities in tonnes, though domestic contracts may still reference the U.S. ton. The U.K. uses the metric tonne in modern trade, with the long ton appearing in historical data.

The USA commonly uses the short ton for domestic sales, yet science, medicine and many industries specify kilograms. In world trade and surface logistics, stating kilograms alongside tons or tonnes helps parties in different systems compare figures.

Writers sometimes use ton to refer to capacity rather than mass. In shipping, tonnage can mean volume, such as a register ton of 100 cubic feet, not weight. For example, a ship’s gross tonnage is measured in register tons of 100 cubic feet each.

NIST notes this dual use in Handbook 44’s General Tables and Units. Always check whether a figure refers to mass or capacity before you calculate freight charges or limits for surface transport.

Use tonne for the metric system and ton for the imperial system. When you must use ton, write short ton or long ton to clarify.

In line with “ton vs” and “ton and tonne” search habits, add the metric equivalent in kg for clarity. This approach reduces confusion in contracts, invoices and specs.

When measuring weight for global trade, always state the unit and, in parentheses, the equivalent in kilograms. Note which systems your readers expect.

In the USA, short tons appear in commodity reports, but international contracts usually specify tonnes. In the UK and Canada, tonnes are standard.

In specs, define terms the first time you use them so readers understand what each unit means on the surface.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.