To find the weighted average cost, divide the total cost of goods available for sale by the total number of units available for sale. This method calculates a cost per unit that reflects the average price paid for all inventory items during a period.
Steps to Calculate Weighted Average Cost:
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Determine the Total Cost of Goods Available for Sale: This involves summing the cost of your beginning inventory and all purchases made during the period.
- Beginning Inventory Cost: The total value of your inventory at the start of the period.
- Purchase Costs: The cost of each purchase you made during the period, including any associated costs like shipping or handling.
The formula for total cost of goods available for sale is:
Total Cost of Goods Available = (Beginning Inventory Cost) + (Cost of Purchases)
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Determine the Total Units Available for Sale: This involves summing the number of units in your beginning inventory and the number of units purchased during the period.
- Beginning Inventory Units: The number of units you had in stock at the start of the period.
- Purchased Units: The number of units you purchased during the period.
The formula for total units available for sale is:
Total Units Available = (Beginning Inventory Units) + (Purchased Units)
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Calculate the Weighted Average Cost: Divide the total cost of goods available for sale by the total number of units available for sale.
Weighted Average Cost = (Total Cost of Goods Available) / (Total Units Available)
Example:
Let's say a company has the following inventory data:
- Beginning Inventory: 100 units at \$10 each (Total Cost = \$1,000)
- Purchase 1: 200 units at \$12 each (Total Cost = \$2,400)
- Purchase 2: 150 units at \$15 each (Total Cost = \$2,250)
Here's how to calculate the weighted average cost:
- Total Cost of Goods Available: \$1,000 + \$2,400 + \$2,250 = \$5,650
- Total Units Available: 100 + 200 + 150 = 450 units
- Weighted Average Cost: \$5,650 / 450 = \$12.56 per unit (approximately)
Therefore, the weighted average cost of each unit in inventory is \$12.56. This cost is then used to value the cost of goods sold and ending inventory.
Why Use Weighted Average Cost?
The weighted average cost method is useful because it:
- Smooths out price fluctuations: It avoids the impact of large price changes on individual sales.
- Is relatively simple to calculate: Compared to other inventory costing methods like FIFO (First-In, First-Out) or LIFO (Last-In, First-Out), it's straightforward to implement.
- Is accepted by GAAP (Generally Accepted Accounting Principles): It's a recognized method for financial reporting.