ABC Classification

Ranking stock by value so attention follows the money

Inventory ControlABC Analysis & Service LevelsFree preview

⏱️ About 15 min

A warehouse can hold thousands of SKUs. Managing every one with equal effort wastes time on items that barely matter. ABC classification ranks stock by how much value it drives, so effort follows the money.

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The big idea: ABC classification (Pareto by annual dollar usage) ranks SKUs by annual demand times unit cost, then takes a cumulative share of total value. Class A items -- about the top 80% of value -- deserve the tightest control; Class B items run to about 95%; Class C items are the long tail. Often a small set of SKUs accounts for most of the value, so a few items deserve most of the attention.

🎯 By the end, you'll be able to

Rank SKUs by annual dollar usage (annual demand x unit cost) and compute the cumulative share of total value.
Classify items as A (cumulative share at or below 0.80), B (to 0.95), or C (the rest).
Explain why Class A items deserve tighter control than Class C items.

📎 Helpful to know first

Comfort with percentages and ranking; no prior module required.

Value first, not SKU count

A buyer who treats 5,000 SKUs identically spreads attention thin. ABC classification applies the Pareto principle to stock: rank every SKU by its annual dollar usage -- annual demand multiplied by unit cost -- and the cumulative share of total value tells you where the money really sits. A small fraction of SKUs usually accounts for most of the value, so the ranking tells you which items deserve tight control and which can be left on autopilot.

\[ \text{Cumulative percent of value} = \frac{\text{running dollar usage}}{\text{total dollar usage}} \]

Reading the formula

Take five SKUs with annual dollar usages of $50,000, $30,000, $12,000, $5,000, and $3,000. Total value = 50,000 + 30,000 + 12,000 + 5,000 + 3,000 = $100,000. Sort from largest to smallest and track the running share: the top SKU is 50,000 / 100,000 = 0.50 of value; the top two reach 80,000 / 100,000 = 0.80; the top three reach 0.92; the top four 0.97; all five 1.00. With Class A drawn at a cumulative share of 0.80 and Class B at 0.95, two SKUs are Class A (80% of value), one is Class B (cumulative 0.92), and two are Class C (0.97 and 1.00).

🔑 The vital few, the trivial many

The standard split puts Class A at a cumulative value share at or below 0.80 and Class B at or below 0.95; the rest are Class C. The payoff is focus: tight controls, frequent counts, and careful forecasting for the few Class A items that drive most of the value; light, automated handling for the long Class C tail. The exact thresholds are conventions -- 0.80 and 0.95 are common, not laws -- chosen to fit how lumpy the value distribution actually is.

🎮 ABC Classification Explorer LIVE

Predict first: Predict first: with usages $50,000; $30,000; $12,000; $5,000; $3,000, how many SKUs are Class A and what share of value do they hold?

Slide the Class A and Class B thresholds to watch SKUs move between bands.

📝 Worked example: A catalog has five SKUs with annual dollar usages of $50,000; $30,000; $12,000; $5,000; and $3,000. Using Class A at a cumulative share of 0.80 and Class B at 0.95, classify the SKUs and report the Class-A dollar share.

1. Total value = 50,000 + 30,000 + 12,000 + 5,000 + 3,000 = $100,000.
2. Sorted cumulative shares: 0.50, 0.80, 0.92, 0.97, 1.00.
3. Class A (cumulative share at or below 0.80): two SKUs, holding 80,000 / 100,000 = 0.80 of value. Class B (to 0.95): one SKU (0.92). Class C: two SKUs (0.97, 1.00).

✓ Class A = 2 SKUs (80% of value); Class B = 1 SKU; Class C = 2 SKUs

✏️ Practice: A catalog has annual dollar usages of $45,000; $25,000; $18,000; $8,000; and $4,000. Using Class A at a cumulative share of 0.80, what percent of total annual dollar usage do the Class-A items represent?

💡 Hint

Total the usages, sort descending, and sum the top SKUs whose cumulative share is at or below 0.80.

Solution

1. Total value = 45,000 + 25,000 + 18,000 + 8,000 + 4,000 = $100,000.
2. Sorted cumulative shares: 0.45, 0.70, 0.88, 0.96, 1.00.
3. Class A (cumulative share at or below 0.80): two SKUs (0.45, 0.70), holding 70,000 / 100,000 = 0.70 = 70% of value.

Check your understanding

1. Under the standard ABC rule with a 0.80 threshold, Class A items are those whose cumulative share of annual dollar usage is...

Class A is the top band of value: items whose cumulative share of total annual dollar usage is at or below 0.80.

2. With annual dollar usages of $50,000; $30,000; $12,000; $5,000; $3,000 (total $100,000), the Class-A dollar share is?

The top two SKUs total 80,000 of the 100,000 total, so Class A holds 80% of value.

✅ Key takeaways

ABC classification ranks SKUs by annual dollar usage (annual demand x unit cost) and tracks the cumulative share of total value.
Class A is the top ~80% of value, Class B runs to ~95%, and Class C is the rest.
Effort should follow value: tight control for the vital few Class A items, light handling for the Class C tail.

➡️ ABC tells you which items matter most. The next lesson uses that ranking to count smarter -- counting the important items often and the rest rarely, instead of one exhausting annual wall-to-wall count.

Ready for the next step? Back to the course outline →