Inventory valuation methods: FIFO, LIFO or weighted average?

You hold inventory, and when the accounting period closes a question surfaces: what is it worth, exactly? There is no single answer. Depending on whether you apply FIFO, LIFO or weighted average cost, the same box of goods shows a different value on the balance sheet, and so does your taxable profit. That is the whole point of inventory valuation. Let us walk through each method, compare them on a worked example, and cover what the accounting rules allow in 2026.

What is inventory valuation, exactly?

Inventory valuation is the process of assigning a monetary value to the items you hold, and to each stock issue (a sale or a consumption). It serves two direct accounting needs: recording the value of ending inventory as a balance-sheet asset, and determining the cost of goods sold (COGS) that hits the income statement.

Why do you need a method rather than a simple count? Because your purchases happen at different prices over time. You received a first batch at $10, a second at $12, a third at $14. When you sell one unit, at what cost do you take it out of stock? Since the purchase price is not constant, you need a cost-flow assumption that decides which cost to attach to each issue. That is exactly what FIFO, LIFO and WAC formalize.

Valuation is not the same as the physical count. Counting units is the job of the stock take and day-to-day inventory management. Valuation turns those quantities into dollars. The two are linked: a wrong count corrupts the valuation, and a sloppy valuation distorts the profit figure.

How does the FIFO method work?

FIFO stands for First In, First Out. The rule is simple: when a unit leaves stock, it is valued at the cost of the oldest batch still available. You use up the earliest purchases first, then move forward in time.

The direct consequence: the items still in stock are valued at the most recent costs, so close to today’s market price. That is one of FIFO’s big strengths, the balance-sheet value tracks economic reality. FIFO also mirrors the natural physical rotation of goods, which makes it a strong fit for perishable products or anything with an expiry date, where you obviously move the oldest stock first.

How does the weighted average method work?

The weighted average cost (WAC) method attaches to each issue an average cost, computed by weighting the quantities and values that entered stock. You stop distinguishing batches: all costs are blended into a single average, recalculated whenever new stock arrives.

The formula is direct: WAC = (value of existing stock + value of new purchases) ÷ (quantity on hand + quantity received). Each unit that leaves is then valued at that average cost, until the next receipt updates it. There are two variants: the moving average (recalculated after every receipt) and the periodic weighted average (one average over the month or the year), simpler but less precise.

The appeal of WAC is that it smooths price swings. Neither profit nor stock value is sensitive to a one-off, more expensive batch. That is why it suits non-perishable raw materials and interchangeable items bought continuously, where tracking each individual batch would make little sense.

What about LIFO, and where is it allowed?

LIFO (Last In, First Out) applies the reverse logic of FIFO: issues are valued at the cost of the most recent batches. In an inflationary period, that raises COGS, lowers reported profit and therefore tax, while leaving on the balance sheet a stock valued at old, often understated costs.

This tax advantage is why LIFO remains permitted in the United States under US GAAP. But IFRS bans LIFO under the revised IAS 2 standard, so companies reporting under international standards (most of the world outside the US) cannot use it. Practically, LIFO is a US-only option, and only worth it if you are US-based and can handle its extra complexity.

FIFO vs weighted average: what does a worked example show?

Take a simple case. You make three receipts, then sell 250 units:

The pattern is clear: with rising purchase prices, FIFO values ending inventory higher ($700 vs $600) and leaves a lower COGS, so a higher reported profit. WAC smooths everything to $12. Over a single month the gap looks tiny, but multiplied across thousands of SKUs and a full year, it shifts tens of thousands of dollars of taxable profit. Hence the need to choose deliberately, then stick to it.

Which inventory valuation method should you choose?

No method is “best” in the abstract. The choice depends on your business, your constraints and one key accounting principle, consistency: once chosen, the method must stay the same from one period to the next, otherwise your financials stop being comparable. Here are the markers:

• Pick FIFO if you handle perishable or dated products (food, cosmetics, pharma), or if you want a balance-sheet stock close to current prices. It is the most intuitive and the most auditable method.
• Pick weighted average (WAC) if you handle non-perishable raw materials or interchangeable items bought in a continuous flow, and you want to smooth the effect of price swings on your profit.
• Skip LIFO unless you report under US GAAP: it is banned under IFRS, whatever tax benefit it might deliver elsewhere.

Either way, valuation is not designed in isolation. It rests on reliable counts, tight flow tracking, and indicators like the inventory turnover ratio or an ABC analysis to focus effort on the SKUs that matter. If you are starting from scratch, our guide on how to manage inventory lays the groundwork before valuation.

How does an ERP compute inventory valuation?

On a handful of SKUs, a spreadsheet does the job. The moment the catalog grows and receipts and issues multiply every day, manual calculation becomes unworkable and error-prone. That is where the ERP steps in: its inventory module automatically applies the configured method (FIFO or average cost), recomputes the cost on every movement, and pushes the figure into accounting with no re-keying. If the concept is new to you, our primer on what an ERP actually is sets the scene.

In practice, an ERP guarantees three things a spreadsheet cannot sustain: consistency between the valued physical stock and the accounting entries, full traceability of every movement, and a constant method across the whole period. On tools, open-source ERPs concentrate most searches. Odoo natively handles FIFO and average-cost valuation in its Inventory app, with a One App Free plan limited to a single app, then a Standard plan around $24.90 per user/month billed annually that unlocks every app (indicative US pricing, July 2026, check odoo.com/pricing since Odoo adjusts rates once or twice a year). ERPNext is free when self-hosted under GPL, with managed Frappe Cloud from around $5/month. Heavier suites such as SAP Business One and NetSuite stay on a custom quote through an integrator. The integration line (importing items, configuring the method, training) often weighs more than the license itself.