Looking at whether a thread is male or female as well as tapered or parallel is important, but these are not the only ways to distinguish between thread types. Pitch size and diameter are also important factors to consider when purchasing or using a threaded part. The pitch size of a thread can either be the number of threads per inch or the distance between each specific thread, depending on whether you are using the imperial or metric measurement system, respectively. The pitch size of a thread is usually measured using a pitch gage. The diameter of a thread is simply the internal (when female) or external (when male) diameter across the edges of the thread. Thread diameter is important when determining whether the thread is tapered or parallel.