"How many coffees do you drink?"
Translation:Quanti caffè bevi?
'Quanti' and 'quante' both mean 'how many'. 'Quanti' is masculine; 'quante' is feminine.
e.g. Quanti libri leggi. Quante mele mangi.
'Quanto' and 'quanta' both mean 'how much'. 'Quanto' is masculine; 'quanta' is feminine.
e.g. Quanto zucchero mangi. Quanta acqua bevi (or quant'acqua bevi).
In English we usually say, "How many cups of coffee do you drink?" The given sentence (how many coffees) is not what most people would say. But when I translated "Quanti caffè bevi?" by "how many cups of coffee...." I was told it was wrong because I made coffee singular.
"Caffi" doesn't exist. (Maybe it's a family name, but not a word.)
"Caffè" doesn't change with the plural. I think all the words ending with an accent (and with consonant) don't change with the plural.
Il caffè -> i caffè
La verità -> le verità
Il gas -> i gas
Il neon -> i neon
L'hotel -> gli hotel
Il comò -> i comò
I cannot say, "How many coffees . . .?" in my native English language even in conversation, because in my head I would be correcting the incorrect English grammar. Coffee is a non-countable noun. Cups of coffee are countable. Liquids (milk, water) are one type of an uncountable noun. .
They match the thing they are describing the quantity for in gender (masculine and feminine) and number (singular and plural). So here it is "coffees" (caffè), which is masculine plural.
"Quanto" and "quanta" are singular, so they usually go with uncountable things (things you can't count) and mean "how much":
Quanta farina? How much flour? ("Farina" is feminine, so you use the feminine singular.)
Quanto zucchero? How much sugar? ("Zucchero" is masculine singular.)
"Quanti" and "quante" are used for countable things, meaning "how many":
Quanti uomini? How many men? ("Uomini" is masculine plural.)
Quante donne? How many women? ("Donne" is feminine plural.)