Comment by ThomasMidgley

"Also, depending on the ingredient, it makes more sense to use cups as a measurement of volume, not mass, when converting to metric."

Hmmm... What kind of cup? :-)

US "legal" cup (240ml)

US customary cup (246,6ml)

metric cup (250ml)

UK cup (170,5ml)

edit: fixed typo 150ml -> 250ml