The size of the field, when soccer was first introduced, was not defined and even the layout could be different even within the same country, which practically meant that someone could play in a field of 80yards and someone else in a 100yards. This fact was not only weird but also unfair for the players, so the first Association of Soccer, founded by the British in the 19th century, introduced the first guidelines for the appropriate length, and years later FIFA established the rules and exist currently.
Even now though the existing rules permit some kind of variation when it comes to size : the field has to be rectangular ( this rule cannot change and does not underlie to any kind of variation ), the length cannot be less than 100 yards (90 m), and no bigger than 130 (120 m) and its breadth cannot be less than 50 (45 m), and no more than 100 yards (90 m) . For international games this is a little more limited: length cannot be more than 120 yards (110 m) nor less than 110 yards (100 m), and the breadth not more than 80 yards (75 m)nor less than 70 yards (64 m).
In any case though, the length must always exceed the breadth. In modern soccer though rarely can someone see that big variations, so more or less all fields have approximately the same size without reaching the maximum suggested and allowed. The size though has to be reduced when it comes to women soccer or to fields allocated for players under the age of 16 or those with disabilities.
Except for the outer lines size there are rules that apply to the inner lines of the soccer field as well. According to those, the field is separated by a central line, which has the exact same distance from the each of the width end. There is always a circle, located at the middle of this line and its diameter has to be 10 yards.
Goal posts are placed at the middle of each pitch width and have to be 24 feet wide and 8 feet high and they are surrounded by two rectangular boxes: the bigger one, called penalty box since every foul in this area leads to penalty kick, is 18 yards wide and 44 long.
The small box, called protection area, is 6 yards wide and long. One more interesting rule about the size of the interior lines of the field is that around the corner ends there is a flag set in a circle of 1 yard (.914m) diameter - this is where the corner kick takes place.
There are many researches and analysis about the soccer field length; most of them converge at the point that larger fields are more suitable for players with better stamina and those speedy ones who tend to kick the ball forward and run, making it hard for defenders, while the smaller ones are and allow more touches and bigger fun (that is why recreational and not professional ones are usually smaller).
In a larger field players have to run more which can affect their game play since they can be easily worn out and end up playing with long kicks and make the game boring and degenerated. Longer and bigger fields demand a better coordination and coverage between the lines from the teams, otherwise the opponents have better chance to organize their game and reach the goalposts becoming dangerous.