3 - One on the field and 2 side refs.
ACTUALLY, there are four. 1 main one, 2 assistants on the sideline, and one ref that manages the subs or coaches.(the guy who holds up the board)
In professional soccer, usually just one on the pitch. There are also two linesmen.
The Laws of the Game specify a Referee, two Assistant Referees and a Fourth Official. But they are not on either of the competing teams. They form their own "team" and it's the one responsible for administering the game. Many games (if not most) operate with three officials, and there are no problems. The fourth official is there in case one of the three assigned to cover the game cannot due to injury, illness or the like, and that fourth official also handles all the substitutions from a point at the middle of the field on the side where the teams are positioned. Substitutions can be handled by three officials with little impact on the game. In a pinch, two officials can officiate a match (but never a professional or international match) and do quite well. During the "soccer explosion" of the past decade or two, there was a dearth of officials and many recreational games and some competitive games were run by a pair of referees. There are a couple of different "set-ups" for two officials (called a "duel"). They are 1) a center referee and one assistant on one of the sides, and 2) two referees on the field of play. With a pair of savvy officials, this will adequately provide for the administration of the game, though it isn't "policy" to officiate games in this manner. Or there could be a dozen referees on the field. How so? It is possible that many or even most of the players on both sides of, say, two vying under-16 competitive soccer teams who are playing against each other are registered and active soccer referees (and are even coaches) who officiate (or coach) at youth (U-6, U-8, U-10) games when they are not playing. Many competitive teams have coaches (who are registered and active officials) who encourage their players to take a referee's course, pass it and get certified and actually officiate at youth games to improve their own knowledge of the rules and give something back to the game. In a U-16 match between two competitive teams, there may be a dozen "referees" on the field. No problem.... Hey, you asked.
There is three official referees, one running on the field and one on each sideline. They do have a reserve/4th ref who is out of the field. Currently there is an experiment with an extra referee behind the goals.
There is one main referee, who is on the field, and there are two assistant referees, also known as "linesmen" - one on each side of the field who help determine if the ball has crossed the end line on their half.
There may also be a 3rd and 4th assistant referee - in that case, they are probably the ones who stand behind the goal and help determine if the ball has crossed the goal-line or not.
the average number in the little league is two
At least 3, sometimes more depending on location
There is 1 referee on a soccer field. Three others are along the touch lines, two assistants and a fourth official.
3 referees are in soccer and football
One referee 2 assistant referees and in senior league games a 4th official who monitors subs and time management
They are technically called assistant referees.
Soccer referees are graded by levels, not by classes. Informally, a referee might be considered "Class A" if they are certified International referees.