Which method of measuring is best used for a piece of pipe that will have fittings screwed on only one end?

The best method for measuring a piece of pipe that will have fittings screwed on only one end is to measure from the end to the center. This approach is particularly useful because it provides accurate information on how far the fitting will extend from one end of the pipe, which is critical for ensuring that the installed components fit correctly in a plumbing or piping system.

By determining the measurement from the end of the pipe to the center, one can effectively account for the connection point of the fitting, which is vital when planning installations. This method ensures that there is no discrepancy between the length of the pipe and the space required for the fitting, thus facilitating precise assembly and installation.

Other methods, such as measuring from the outer diameter to the end or using inner diameter measurements, would not provide the needed reference for fitting connections when only one end is involved. Center to center measurements are typically applicable in situations where both ends need to be aligned or connected to other fixtures, which doesn't apply in this specific scenario. Hence, measuring from the end to the center aligns well with the practical needs of the installation.