Quante olive servono per fare 1 litro di olio?
The “yeld” of olives in e.v. olive oil is usually expressed in Kilograms and, specifically, per 100 kg of olives (moral: how many litres of olive oil do you get from milling 100 kg of olives).
So: if I get 15 kg of olive oil from pressing 100 kg of olives, it means that the yield of those olives was 15 (15%). We can then say that for 1 L of oil I might need about 7 kg of olives.