公吨（Tonne）是公制的质量单位，简写为t。其虽非国际单位制（SI）基本单位之一，但符合十进制，在使用上是可以与国际单位制相合。

1公吨（1,000公斤；2,200英磅）

(1 metric ton = 1,000 kilograms = 2204.62 avoirdupois pounds.) Metric Ton

吨也是最大的通用国际标准计量单位。数量巨大时，常以千的倍数如千吨、百万吨来计量，中文则还以万的倍数如万吨、亿吨来计量。在英国，公制的顿于英文中常写为tonne或MT（metric ton），以便与吨（ton，即long ton，长吨、英吨）有所区别。

The tonne (/tʌn/) (British and SI; SI symbol: t) or metric ton (in the United States) is a non-SI metric unit of mass equal to 1,000 kilograms; or one megagram (Mg); it is equivalent to approximately 2,204.6 pounds, 1.10 short tons (US) or 0.984 long tons (imperial). Although not part of the SI per se, the tonne is "accepted for use with" SI units and prefixes by the International Committee for Weights and Measures, along with several other units like the bar, litre and day.