The X-Factor, sometimes called the uncertainty factor, is a variable used in inventory forecasting and safety stock calculations to account for unpredictable changes in demand or supply conditions. It represents the unknown or unexpected fluctuations beyond historical trends. Incorporating the X-Factor into inventory models helps companies build buffers against volatility, reducing stockouts and enhancing service levels. However, excessive conservatism can lead to high carrying costs, so balancing the X-Factor is key to effective inventory optimization.