Enter Inventory Data

Beginning Inventory
Units on hand
$
Per unit cost
Purchase 1
Units purchased
$
Per unit cost
Purchase 2
Units purchased
$
Per unit cost
Purchase 3
Units purchased
$
Per unit cost
Total units sold during period
%
Enter as percentage (e.g., 21 for 21%)
Key Formulas
FIFO: Oldest costs → COGS
LIFO: Newest costs → COGS
WA: Total Cost / Total Units
LIFO Reserve = FIFO EI − LIFO EI
Tax Impact = (LIFO COGS − FIFO COGS) × Tax Rate
Ryan O'Connell, CFA
Calculator by Ryan O'Connell, CFA

Goods Available for Sale

Total Units --
Total Cost --
Avg Cost/Unit --

Method Comparison

Metric FIFO LIFO
Cost of Goods Sold -- -- --
Ending Inventory -- -- --

LIFO Reserve & Tax Impact

LIFO Reserve --
FIFO EI − LIFO EI
Tax Impact (LIFO vs FIFO) --
Positive = LIFO saves taxes

Layer-by-Layer Detail

Formula Breakdown

Understanding Inventory Valuation Methods

Why Do Inventory Methods Matter?

The choice of inventory cost flow method directly affects a company's reported cost of goods sold, ending inventory, net income, and tax liability. Under U.S. GAAP, companies may choose FIFO, LIFO, or Weighted Average. Each method allocates the same total cost differently between COGS and ending inventory.

Fundamental Identity
COGS + Ending Inventory = Cost of Goods Available for Sale
This identity holds regardless of the cost flow method used.

Comparing the Three Methods

FIFO

First-In, First-Out
Oldest costs go to COGS. Ending inventory reflects recent prices. Higher income when prices rise.

LIFO

Last-In, First-Out
Newest costs go to COGS. Ending inventory reflects older prices. Lower taxes when prices rise.

Weighted Average

Average Cost Method
Blends all costs into a single per-unit average. Smooths price fluctuations. Same result under periodic and perpetual for WA.

LIFO Reserve & Tax Implications

The LIFO Reserve measures the cumulative difference between FIFO and LIFO inventory values. Companies using LIFO must disclose this reserve (ASC 330). Analysts use it to convert LIFO financials to a FIFO basis for cross-company comparison.

In a rising-price environment, LIFO produces higher COGS and lower taxable income, generating real cash tax savings. However, the IRS LIFO conformity rule requires companies to use LIFO for financial reporting if they use it for tax purposes.

IFRS Note: LIFO is prohibited under International Financial Reporting Standards (IAS 2). Only FIFO and Weighted Average are permitted under IFRS.

Model Assumptions

  • Periodic inventory system — COGS computed at end of period, not per transaction
  • Purchases entered in chronological order (Purchase 1 = oldest, Purchase 3 = newest)
  • FIFO assigns oldest costs to COGS first; LIFO assigns newest costs first
  • Weighted Average uses total cost ÷ total units, applied uniformly
  • U.S. GAAP focused — IFRS prohibits LIFO (IAS 2)
  • Tax impact assumes COGS difference directly affects taxable income
  • For educational purposes only. Not financial advice. Market conventions simplified.

Frequently Asked Questions

FIFO (First-In, First-Out) assigns the oldest inventory costs to cost of goods sold first, while LIFO (Last-In, First-Out) assigns the newest costs first. In a rising-price environment, FIFO results in lower COGS and higher net income, while LIFO results in higher COGS and lower taxable income. FIFO is allowed under both U.S. GAAP and IFRS, while LIFO is only permitted under U.S. GAAP.

The LIFO Reserve is the difference between inventory valued under FIFO and inventory valued under LIFO (LIFO Reserve = FIFO Inventory − LIFO Inventory). Companies using LIFO are required to disclose this reserve, which allows analysts to convert LIFO financial statements to a FIFO basis for comparison. A growing LIFO Reserve generally indicates rising inventory costs, though changes can also reflect quantity fluctuations and LIFO liquidations.

The Weighted Average method calculates a single average cost per unit by dividing the total cost of goods available for sale by the total units available. This average cost is then applied uniformly to both COGS and ending inventory. It smooths out price fluctuations and is simpler to apply than FIFO or LIFO, especially with many purchase layers.

When prices are rising, LIFO assigns the higher, more recent costs to COGS, resulting in higher expenses and lower taxable income. The tax savings equal the COGS difference between LIFO and FIFO multiplied by the tax rate. However, the IRS requires companies using LIFO for tax purposes to also use it for financial reporting (the LIFO conformity rule).

This calculator uses the periodic system, where COGS is computed at the end of the period using all available inventory layers. Under a perpetual system, COGS is calculated with each individual sale transaction, which can produce different results for LIFO and weighted average methods. FIFO produces the same result under both systems.

No. International Financial Reporting Standards (IAS 2) prohibit the use of LIFO. Companies reporting under IFRS may use FIFO or Weighted Average only. This is one of the significant differences between U.S. GAAP and IFRS for inventory accounting. Companies converting from U.S. GAAP to IFRS must adjust their inventory method accordingly.
Disclaimer

This calculator is for educational purposes only and uses simplified periodic inventory assumptions. Actual inventory accounting involves additional complexities such as lower-of-cost-or-net-realizable-value adjustments, LIFO liquidation effects, and perpetual vs. periodic system differences. Consult professional guidance for real-world inventory decisions.

Related Calculators

Bond Amortization Schedule Calculator

Build bond amortization schedules using effective interest method.

Try Calculator →

Depreciation Calculator: Straight-Line, DDB, SYD & Units of Production

Calculate depreciation using straight-line, declining balance, and units-of-production methods.

Try Calculator →

Bad Debt Expense & Allowance Calculator: Aging Schedule Method

Estimate bad debt expense using percentage of sales and aging methods.

Try Calculator →