How Businesses Value Inventory: FIFO, LIFO and Average Cost

Inventory accounting methods are the rules a business uses to decide which costs to assign to the goods it sold during a period and which costs remain on the balance sheet as goods still on hand. When a company buys the same product at different prices over time, it cannot simply read a single cost off a shelf, so it must choose a cost flow assumption. For readers who want to study the subject in a structured way, the Micro Diploma: Inventory Accounting Methods course offers a focused path through these ideas. Getting this choice right matters because it directly shapes reported profit, the value of assets and the amount of tax a business owes.

The three most common approaches are first in, first out (FIFO), last in, first out (LIFO) and weighted average cost. FIFO assumes the oldest units are sold first, so the cost of goods sold reflects older purchase prices and the remaining inventory reflects the most recent prices. LIFO assumes the newest units are sold first, so cost of goods sold reflects recent prices and the remaining inventory reflects older prices. Weighted average cost divides the total cost of goods available for sale by the total number of units, producing one average cost per unit that is applied to every sale and to ending inventory.

The arithmetic is simple, but the effects are not. When prices rise steadily, FIFO usually produces higher reported profit and higher ending inventory values, while LIFO produces lower profit and lower inventory values. Under a perpetual system, the business updates these figures after each sale, while a periodic system calculates them at the end of the period. The method chosen must be applied consistently so that results can be compared from one period to the next.

Consider a small hardware shop with four employees that sells a popular type of cordless drill. It sells 12 drills during the quarter. Under weighted average cost, the average unit cost is 67.50 dollars, so the cost of goods sold is 810 dollars and the ending inventory is valued at 540 dollars.

The owner of this shop would see three different profit figures from the same sales and purchases. A bookkeeper who records each sale when it happens can apply FIFO or average cost with a running balance, which suits a shop that tracks individual items. A shop that counts stock only at the end of each month may find that a periodic average method is simpler to maintain with a small team.

No single method is correct in every situation, and each has trade-offs. LIFO better matches current costs against current revenue during rising prices, but it can leave inventory values on the balance sheet far below current cost and is not permitted under International Financial Reporting Standards. Weighted average cost smooths price swings and is simple to apply, though it can blur the cost of specific units.

The main takeaway is that inventory method choice affects comparability, reporting rules and tax outcomes, so businesses should understand the rules that apply in their jurisdiction and apply their chosen method consistently. Future practice is likely to continue emphasizing accurate, timely records, since better data makes any of the three methods more reliable.