Generally speaking, the duration of a soccer game is 90 minutes, consisting of two equal halves lasting 45 minutes each. This is commonly referred to as 'regulation time'. With 45 minutes a half and few breaks in play, soccer is a true game of endurance and skill.
In each game of soccer, there is a halftime interval which usually lasts 15 minutes, but can occasionally be shorter at the discretion of the referee - shorter halftime intervals are more common at amateur level, where TV broadcasts are not a consideration.
It should be noted that the length of time a game continues for depends on the competition rules and the context of each game. So, for example, in some knockout tournaments, if the game is tied after regulation time, 'extra time' (see below) is played. This is a period of 30 minutes after regulation time that is split into two 15-minute halves.
If, for whatever reason, the game is interrupted, then the referee can add time - this is known as 'added time' or 'injury time' (see below). In some cases, referees have added up to 10 minutes of time at the end of games, meaning the actual duration of a match can sometimes be closer to 100 minutes.
In the event that the game remains tied after extra time, then penalty kicks are usually used to decide the winner. The duration of a penalty kickout varies and continues until a winner has been determined.
Taking into account all of the above to give you an example, if an ordinary league game (with no extra time) kicks off at 3pm, then, including halftime, it will be over at approximately 4:45pm - a duration of roughly one hour and 45 minutes.
If a knockout game begins at 3pm and is decided in extra time, it will be over at approximately 5:30pm. Got it?