Moving Average Cost
Also called: moving average costing, rolling average cost
What is Moving Average Cost?
Moving average cost values stock at a running blended average rather than at the rate of the most recent purchase. Each time stock arrives at a different rate, the average is recalculated across the quantity already on hand and the quantity received, and that new average is what is charged out to cost of sales until the next receipt moves it again.
Why it matters to your margins
The gap between the invoice rate and the blended average is the reason recipe and product costs drift out of true. When a rate falls, costing at the new invoice rate understates what is actually in your bin. When a rate rises — the more common and more damaging case — costing at the old average flatters your margin until the cheaper stock runs out. Neither error announces itself; both show up later as a gross margin that does not match the arithmetic.
How it compares to the alternatives
Against first-in-first-out, moving average smooths the effect of a price spike rather than passing it straight into cost of sales, which makes month-to-month margins more comparable but slower to reflect reality. Against standard costing, it tracks actual purchase behaviour instead of a fixed planning rate, which means it will not by itself tell you that a supplier has crept up on you — that needs a variance comparison against a baseline you set.
Practical cautions
Three things break a moving average in practice. Receiving in a different unit from the one you issue in corrupts the average silently. Entering a bill without its freight or duty gives you an average below true landed cost. And a negative quantity on hand, which happens when issues are recorded before receipts, produces an average that is arithmetically meaningless until the sequence is fixed.
Frequently asked questions
For reporting what a period actually cost, the blended average is the truer figure because it reflects the stock you consumed. For deciding what to charge going forward, the latest rate is the more useful signal, since it is what the next batch will cost you.