A sheep or goat is used as a single offering and is sufficient for one household;
Abu Ayyoob al Ansaree (may Allaah be pleased with him) said:

“At the time of the Messenger of Allaah (peace and blessings of Allaah be upon him), a man would sacrifice a sheep on behalf of himself and the members of his household, and they would eat from it and give some to others.” (Reported by Ibn Maajah and al-Tirmidhi, who classed it as saheeh) … More EID AL-ADHA SACRIFICE