Kong-chhioh ia̍h bí-ta̍t, bí, sī leh niû tn̂g-té ê tan-ūi, i sī SI ki-pún tan-ūi chi it, kì chò m. Pún-té Hoat-kok Kho-ha̍k-īⁿ (French Academy of Sciences) kā chhiah-tō keng-koè Paris kaù pak-ke̍k ê 1/10,000,000 tēng chò 1 bí. Hiān-chhú-sî, Kok-chè Taú-chhìn-chhioh Kio̍k (International Bureau of Weights and Measures) kā kng tī chin-khong 1 bió-cheng chaú ê kī-lî ê 1/c tēng chò 1 bí.
1 bí iok-liōng 3.28 eng-chhioh. Kā m thaû-chêng ke SI jī-thaû (SI prefix) ē-tàng tit tio̍h chit-koá tn̂g-té ê cho͘-ha̍p tan-ūi, pí-lūn kóng 1 km tō sī 1 kong-lí = 1000 m, 1 cm tō sī 1 kong-hun = 1/100 m.
