～くらい; ぐらい
～くらい; ぐらい · ～kurai; gurai · JLPT N5 · noun
approximate (quantity)
📏 kurai = 位 (rank, position): about the rank of X, so roughly X
くらい comes from the noun 位 (kurai), meaning rank or grade. Saying 100円くらい places an amount at about that grade, hence roughly. ぐらい is the same word with the k voiced to g after another word; both forms are interchangeable.