When using football fields as a unit of length you should use American football fields rather than soccer fields because American football field sizes are more standardized.

For American football professional, college, and high school games are all played on the same sized field, which is 100 years long.

Compare to soccer, where they can even have different sized fields in the same professional league. The English Premier League wants to standardize on 105 m x 68 m but several clubs are still using other sizes: Brentford (105 x 65), Chelsea (103 x 67), Crystal Palace (100 x 67), Everton (103 x 70), Fullham (100 x 65), Liverpool (101 x 68), and Nottingham Forest (105 x 70).

For international play FIFA has a standard, but it is a range: 100-110 m x 64-70 m.

There are parts of a soccer field that are precisely specified and so could be used as a standard of length.

Some examples are the radius of the circle around the center mark (9.144 m), the penalty area (40.23 x 16.46 m), distance from penalty mark to goal (10.97 m), goal area (18.29 m x 5.47 m), distance between goal posts (7.32 m), and the height of the crossbar (2.44 m).

The reason none of them are nice integers is that they were actually originally standardized in Imperial units. In those the aforementioned measurements are 10 yards, 44 yards x 18 yards, 12 yards, 20 yards x 6 yards, 8 yards, and 8 feet, respectively.