The weighted average method is a trend prediction method, which uses several observation values of the same variable arranged in time sequence in the past, and takes the time sequence number as the weight to calculate the weighted arithmetic average of these observation values, and takes this number as a prediction value of the variable in the future.

The weighted average method can calculate the weighted average unit price of the inventory at the end of the current period according to the quantity and amount of the inventory at the beginning and the quantity and amount stored in the current period, which can be used as the price and actual cost of the inventory issued at the end of the period.