Before jumping into the answer, let us turn your attention to the results of not choosing the right size. Every mechanic who didn’t pick their plumber spanner right has a story of injury, be it scars or bruised knuckles from due to a slippery wrench. Sometimes, the pipe might break and worsen the situation even more.
For someone who intends to build a toolbox for home use, 14-inches would be perfect pipe wrench size. The weight is light and suitable to carry around. As for more sophisticated home and industrial use, an 18 inches pipe wrench should be able enough. Remember, this wrench can work with piping up to 2.5 inches diameter.
If you’re sure you have to work with wider pipes, feel free to choose from bigger sizes. There’s no scarcity of options. You can get sizes up to 60 inches.
If you have to work with varying sizes, choosing an adjustable pipe wrench is the right course of action.