Siong-tùi goân-chú chit-liōng (Eng-gí: relative atomic mass, kán-lio̍k: r.a.m., hû-hō: Ar), a̍h sī kóng goân-chú tāng-liōng (atomic weight, thoân-thóng hoan-e̍k: goân-chú-liōng) sī chi̍t khoán thian-jiân chûn-chāi ê goân-sò͘ goân-chú, i pêng-kin bí lia̍p ê chit-liōng kap 12C goân-chú chit-liōng ê 1/12 chi kan ê pí-lē.