What Is ABC Inventory Analysis?
ABC inventory analysis ranks products by their contribution to revenue, then groups them into A, B, and C categories. It helps Shopify merchants decide which SKUs need close stock control and which may be tying up cash without generating much revenue.
A-items usually represent a small share of SKUs but most sales; C-items make up a larger share of the catalog but contribute less revenue. These proportions are starting points, not fixed rules: a low-revenue accessory may still support sales of a best seller, so review product relationships before discontinuing it.
ABC Inventory Analysis Formulas
SKU Revenue Share = SKU Revenue ÷ Total Annual Revenue × 100
Cumulative Revenue Share = Running Total of SKU Revenue ÷ Total Annual Revenue × 100
GMROI = Annual Gross Profit ÷ Average Inventory Value at Cost
Annualized Holding Cost = Inventory Value at Cost × Monthly Holding Rate × 12
Average Revenue per SKU = Total Annual Revenue ÷ Total SKUs
To assign categories, sort SKUs from highest to lowest annual revenue and calculate cumulative revenue share. Under the common Pareto-based setup, A-items account for roughly the first 80% of revenue, B-items for the next 15%, and C-items for the remainder. The calculator uses your entered SKU and revenue percentages to estimate category-level results; actual SKU-level classification requires individual product revenue data.
How to Use This Calculator
- Enter Total SKUs — the number of active products or variants you want to analyze. Use the same definition of SKU that you use in Shopify reports.
- Enter Total Annual Revenue — sales revenue across those SKUs for a representative 12-month period. Use net sales consistently if you exclude discounts and refunds.
- Enter Total Inventory Value — the cost value of the inventory being analyzed. For a GMROI estimate, use average inventory at cost over the year when available, rather than a single unusually high or low snapshot.
- Enter Average Margin % — your average gross margin across the products in scope. This lets the tool estimate gross profit from revenue.
- Enter Monthly Holding % — the monthly cost of carrying inventory, including expenses such as storage, insurance, and tied-up capital. Use your own estimate; 2–3% per month is a common planning assumption, not a universal rate.
- Set the A, B, and C SKU and revenue percentages — enter A %, A Revenue %, B %, B Revenue %, C %, and C Revenue % to reflect your classification model. Check that the SKU percentages and revenue percentages each total 100%.
- Review the results — compare revenue per SKU, estimated GMROI, holding costs by class, and C-item optimization scenarios. Adjust the category assumptions to test how different cutoffs change the picture.
Step-by-Step Example
Suppose a Shopify store has 500 active SKUs, $800,000 in annual revenue, and $150,000 in average inventory at cost. Assume a 55% average gross margin and a 2.5% monthly holding rate.
| Calculation | Arithmetic | Result |
|---|---|---|
| Average revenue per SKU | $800,000 ÷ 500 | $1,600 |
| A-item SKU count | 500 × 20% | 100 SKUs |
| A-item revenue | $800,000 × 80% | $640,000 |
| B-item SKU count and revenue | 500 × 30%; $800,000 × 15% | 150 SKUs; $120,000 |
| C-item SKU count and revenue | 500 × 50%; $800,000 × 5% | 250 SKUs; $40,000 |
| Estimated annual gross profit | $800,000 × 55% | $440,000 |
| Estimated GMROI | $440,000 ÷ $150,000 | 2.93 |
| Monthly holding cost | $150,000 × 2.5% | $3,750 |
| Annualized holding cost | $3,750 × 12 | $45,000 |
The average revenue per SKU hides substantial differences: the estimated A-item average is $640,000 ÷ 100 = $6,400, while the C-item average is $40,000 ÷ 250 = $160. The overall GMROI is a portfolio-level estimate; use SKU-level cost and sales data to identify which products have the strongest returns.
Interpreting ABC Results and GMROI
ABC rank measures revenue contribution, while GMROI measures gross profit earned per dollar invested in inventory. A high-revenue A-item can still have weak GMROI if it has a low margin or requires unusually large stock. Conversely, a lower-revenue item may deliver a strong return if it sells at a healthy margin and turns quickly.
| Category | Common planning range | Inventory decision |
|---|---|---|
| A-items | About 4–8 GMROI | Monitor frequently, prioritize replenishment, and protect availability. |
| B-items | About 2–4 GMROI | Review reorder quantities and watch for movement into A or C. |
| C-items | Aim for at least 1 GMROI | Reduce excess stock, test bundles, or assess discontinuation. |
These are practical targets, not guarantees or industry-wide laws. Compare results with your own history and product economics; retail inventory patterns vary by sector, as shown in the U.S. Census Bureau’s retail sales and inventory data. For more detail on carrying costs such as storage, insurance, and obsolescence, use the Inventory Carrying Cost Calculator. The Inventory Turnover Calculator can help you compare GMROI with turnover and days-in-inventory measures.
Industry Benchmarks and Classification Limits
The familiar 80/15/5 revenue split is a useful starting model, but actual distributions depend on catalog size, price points, seasonality, and product mix. The table below describes the common allocation—not a required result for every store.
| Class | Approximate share of SKUs | Approximate share of revenue | Typical management focus |
|---|---|---|---|
| A | 20% | 80% | Frequent review and tighter service-level controls |
| B | 30% | 15% | Regular review and proportionate replenishment |
| C | 50% | 5% | Lean stock and periodic assortment review |
Treat these percentages as adjustable thresholds. A seasonal store may classify products using the relevant season’s sales, while a new store may need a shorter analysis period until a full year of sales is available. The Small Business Administration’s financial management guidance also emphasizes keeping reliable financial records; accurate sales and cost data make inventory comparisons more useful.
6 Tips to Optimize Your Inventory Mix
- Change your review period from 12 months to 90 days for a fast-changing product line, then compare category shifts. A shorter window reacts faster but can overstate temporary promotions or seasonal spikes.
- Test a higher A-item threshold, such as 75% rather than 80% of revenue, and see which additional SKUs receive tighter monitoring. This can be useful when stockouts on near-A products are costly.
- Reduce C-item reorder quantities by 25% in a test group and monitor stockouts and sales for one replenishment cycle. Use a Reorder Point Calculator to set replenishment triggers around supplier lead time.
- Compare a C-item bundle with a standalone listing. Pair a slow-moving accessory with a popular product and measure whether the bundle raises order value without discounting the main item excessively.
- Reclassify before and after peak season if demand changes sharply. Products that were A-items during a holiday rush may require lower reorder quantities once demand normalizes.
- Separate dead stock from ordinary C-items. Change the review rule to flag products with no sales in 90 days, then compare markdown or liquidation options with continued storage using the Dead Stock Identifier.
Frequently Asked Questions
What is ABC inventory analysis?
ABC inventory analysis classifies products into three categories based on revenue contribution: A-items are the top ~20% of SKUs generating ~80% of revenue, B-items are the middle ~30% generating ~15%, and C-items are the bottom ~50% generating ~5%. This Pareto-based model helps merchants focus stock controls and replenishment attention where sales are concentrated, but the proportions should be adjusted to fit the business.
How do you calculate ABC classification?
- List every SKU with its revenue for the analysis period.
- Sort the SKUs from highest revenue to lowest.
- Calculate each SKU’s revenue share and the cumulative revenue share.
- Assign A, B, and C classes at your chosen cumulative-revenue cutoffs.
In Shopify, export a product sales report and calculate the running revenue total; adjust the cutoffs if your catalog does not follow the usual distribution.
What should I do with C-items?
Reduce exposure before removing products: try smaller order quantities, made-to-order or dropship fulfillment, bundles, or a price test. Check whether an item supports sales of an A-item, such as a compatible accessory, before discontinuing it; also compare its GMROI and storage cost with the revenue it contributes.
How often should I update ABC classifications?
Reclassify quarterly for a stable catalog, and before and after major selling seasons for seasonal products. Watch for B-items gaining momentum, A-items declining, and new products with rapidly rising sales; some stores also track a separate dead-stock group for products with no sales over a chosen period.
What is GMROI and why does it matter for ABC analysis?
GMROI, or Gross Margin Return on Inventory Investment, measures annual gross profit per dollar of average inventory cost: annual gross profit ÷ average inventory at cost. A result of 3 means the inventory investment generated $3 in gross profit over the period, but it does not by itself account for operating expenses or guarantee net profitability.
Does a C-item always need to be discontinued?
No; ABC classification measures revenue contribution, not strategic value or customer importance. A low-revenue SKU may complete a product range, support a bundle, or generate repeat purchases, so assess those effects and its holding cost before cutting it.
About This Calculator
The ABC Inventory Analysis Tool was built for Shopify merchants by Luis Dev Studio to compare revenue contribution, GMROI, and inventory holding costs. For help applying the results to your store, contact us.
Updated by Luis Gonzalez · Jan 17, 2026