Tan (the letter 擔 was used in Yuan) was a unit of weight (mass) under the Chinese shakkanho (the system of measuring length by the shaku and weight by the kan) (shakusekiho, Chinese traditional system of measurement [unit system], Taiwanese traditional system of measurement).
担（たん、元の用字は擔）は、中国の尺貫法（尺斤法。市制(単位系)・台制）の重量（質量）の物理単位である。