How do you calculate the inventory work in progress in days?

To calculate inventory work in progress (WIP) in days, first determine the average WIP inventory by adding the beginning and ending WIP inventory for a period and dividing by two. Next, calculate the total cost of goods manufactured (COGM) for that period. Finally, divide the average WIP inventory by the COGM per day (COGM divided by the number of days in the period) and multiply by the number of days in the period to get the WIP in days. This gives you an estimate of how long items remain in production before being completed.