Daily Archives: 2nd September

Tons and Tonnes

Every time I see the word “ton” or “tonne” used to describe mass or weight I have to go back and check exactly what the terms mean, so for my sanity and your reference, here is an explanation of the differences.


The long ton is an outdated unit, equivalent to 1016 kilograms, still sometimes used in the UK and in other countries that previously used the Imperial system of measurements.

The short ton is one of the US customary units, equivalent to 907 kilograms. For certain types of measurements (e.g. the tonnage of Navy ships) the long ton is used instead.

The tonne is 1000 kilograms, and is part of the International System of Units, which is why it it often referred to as a metric tonne.

A long ton is 12% larger than a short ton, and 1.6% larger than a tonne. A short ton is 9.3% smaller than a tonne and 11% smaller than a long ton. A tonne is 1.6% smaller than a long ton and 10% larger than a short ton. And if you read that out loud you’ll realise how dangerous using the ton/tonne can be.