ABC Analysis

ABC analysis (also called ABC classification) is an inventory management method that ranks every stock item by its annual consumption value and sorts items into three tiers. The highest-value items sit in Class A. Mid-range items go into Class B. The long tail of low-value items fills Class C. By sorting stock this way, a business stops treating every product identically and directs purchasing attention, stock counting effort, and reorder discipline toward the lines where a stockout or pricing error actually costs money.

The method is grounded in the Pareto principle - the observation that a small number of inputs typically drives the majority of outcomes. In inventory terms, roughly 20% of SKUs tend to account for around 80% of annual inventory value, though the actual split depends on the catalog shape and margin profile of the business.

How to Calculate ABC Classes

The core formula is straightforward: annual consumption value = annual demand x unit cost. Calculate this figure for every SKU, sort them from highest to lowest, then compute the running cumulative percentage of total value down the list.

Assign classes using threshold bands:

• Class A: SKUs covering roughly the first 80% of cumulative annual value - typically 10-20% of total SKUs.
• Class B: The next band from approximately 80% to 95% of cumulative annual value - usually 20-30% of SKUs.
• Class C: The remaining items, often 50-70% of SKUs but contributing only around 5% of annual value.

These thresholds are a starting point, not a fixed rule. A business with a highly concentrated product range may find its A tier is narrower; one with a broad, even spread may need to adjust the cutoffs to reflect how its catalog is actually shaped.

Managing A, B, and C Items Differently

The classification only adds value once it shapes actual operating decisions. Each class should have distinct policies for stock counting frequency, reorder point tightness, and purchasing oversight.

Class A items need weekly stock counts, tight reorder points, and active supplier management. Lead time changes and price fluctuations matter most here. Purchasing decisions for A items should involve human review rather than automatic triggers.

Class B items warrant monthly counts and structured reorder controls. Review them quarterly for reclassification as demand shifts up or down.

Class C items can be managed with quarterly counts and simple min/max replenishment rules. They are also the best candidates for catalog rationalization - slow-moving C items tie up storage space and working capital without contributing meaningfully to revenue.

One important caveat: a low consumption value does not always mean low operational importance. A component or material that halts a job if it runs out is operationally critical even if its annual value sits firmly in Class C. Flagging such items separately ensures they are not under-controlled simply because their unit cost is low.

Businesses managing stock in Zigaflow can track reorder points, monitor purchase order history by SKU, and review stock levels across all product lines - giving the visibility needed to apply A, B, and C policies in practice without maintaining a separate spreadsheet.