Periodic Average Cost
How does periodic average cost differ from moving average costing?
PAC computes one weighted average once per period based on beginning balance, period receipts, overheads, and adjustments, then revalues all transactions for that period. Moving average updates continuously after each receipt or cost event, giving a perpetual running average rather than a period-end blended rate.
What cost elements are included in PAC calculation?
Oracle's PAC formula includes prior period average cost and ending balance, current-period transaction cost and quantity, plus overheads and adjustments. The resulting numerator is divided by the total quantity available in the period, producing a single weighted-average unit cost.
When is PAC most appropriate in supply chain operations?
PAC is best suited when actual costs are known only at period close, such as environments with supplier invoice lag, shared raw-material pools, or production operations that want period-level actual costing instead of transaction-by-transaction updates. It stabilizes unit cost and reduces intra-period price volatility, but requires complete period data before calculation.
Periodic average cost (PAC) is an inventory valuation method that computes a single weighted-average unit cost at the end of a defined period, using beginning inventory, period receipts, overheads, and adjustments. Unlike moving average, PAC is not recalculated after each transaction; instead, all cost-owned transactions are processed, then the resulting period rate revalues inventory, cost of goods sold, and production variances.
On the shop floor, PAC unfolds as a period-end reconciliation event. During the month, material issues to work orders, assembly completions, and raw-material receipts are entered at provisional rates—often prior-period averages or standard placeholders. When financial close begins, the controller runs the PAC calculation after all supplier invoices, freight charges, duties, and overhead allocations are booked. The system pools these costs with beginning inventory and the period's transaction quantities to derive one blended rate for the cost organization and valuation unit. That rate then retroactively revalues everything issued or consumed during the period. Work orders now reflect actual material cost, inventory balances align with paid vendor amounts, and COGS captures true consumption value. In warehouses, PAC smooths fluctuating inbound costs across the period, preventing volatile spot prices from distorting stock valuation. The result: a stabilized, auditable period cost, but only after all transactions are complete and verified.
Late invoices create revaluation shocks: When freight or supplier invoices arrive after issues are posted, the period average shifts, forcing retroactive revaluation of issues and stock. This produces unexpected margin swings and delays close.
Incorrect sequencing corrupts the average: Receipts, returns, negative adjustments, or production outputs must be fully processed before PAC calculation. If not, ending inventory and COGS use an incomplete period pool, yielding a wrong unit cost and variance errors.
Mixed valuation logic breaks reconciliation: When one plant uses PAC and another uses moving average or standard cost, shared materials and intercompany transfers carry mismatched unit costs. This creates reconciliation breaks between warehouse stock, production consumption, and finance ledgers.