First-pass yield is an important manufacturing metric. It measures the effectiveness of a process and provides an indication of how well we are eliminating waste. Other metrics don’t account for the cost of rework, which can be significant at some assembly plants. First-pass yield is also a good measure of the success of continuous improvement activities.
I always like to start with a definition. As an engineer, I like tangible definitions and what better than an equation? First-pass yield is the percentage of parts that are readily usable at the end of a production run. We only need two variables: the number of usable parts (those that do not require rework) and the total number of parts produced. First-pass yield is the ratio of the working parts that come from an assembly line at the end of a run, compared to the total number of parts produced. Put mathematically, first-pass yield = usable parts / total parts built.