The WIP-to-SWIP ratio is a simple comparison of a process, line, or cell’s actual work-in-process (WIP) count vs. its standard work-in-process (SWIP) inventory. Among other things, a process’s target condition reflects the consistent execution of standardized work, including SWIP maintenance (which is why it should be a leader standard-work audit point). No SWIP maintenance, no standardized work adherence. Accordingly, the target WIP-to-SWIP ratio is 1.

A ratio less than 1 indicates that, at least during the time of the WIP count, the WIP level is insufficient. A ratio greater than 1 reflects a situation in which there is excess WIP.

Daily or even more frequent tracking on a run chart or plan-vs.-actual type chart can be incorporated within the natural work team’s visual metrics. Of course, this does not preclude an appropriate andon pull and response. Abnormal conditions should be quickly flagged, and the root causes identified and addressed.

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