Inventory optimization is deciding how much of each product to hold, so the money on your shelves earns as much as it can. The aim is to stop cash sitting in slow stock while best sellers run out. For a small shop, it means measuring what each category's stock earns, then moving cash from the weakest to the strongest.
What is inventory optimization, and how is it different from inventory management?
Inventory management keeps the records: what you hold, what moved, what to reorder. Inventory optimization uses those records to set the targets: how much of each product, in which branch.
Two costs pull in opposite directions.
Holding too much costs cash, space and spoilage (inventory holding cost). Holding too little costs sales you never make. Optimization finds the level where the two together are smallest.
How do you measure whether your inventory is optimized?
With four numbers per category, worked out from your sales and stock records for the same period. The table gives each formula.
| Number | Formula | What it tells you |
|---|---|---|
| GMROI (gross margin return on inventory) | Gross profit ÷ average stock at cost | What each naira of stock earned in the period |
| Inventory turnover | Cost of goods sold ÷ average stock at cost | How many times the stock sold through |
| Days of stock | Days in the period × average stock ÷ cost of goods sold | How long the stock sits before it sells |
| Dead stock share | Stock unsold for 90 days ÷ all stock, at cost | How much cash is stuck |
The turnover formula is the standard one (Corporate Finance Institute), and inventory turnover covers it in detail. CFI warns that ratios only compare fairly within the same industry. A small shop can go further and compare its own categories, which share a building, a till and an owner.
For example: a scorecard for a mini-mart in Ibadan
Take a mini-mart in Ibadan with ₦7,500,000 of stock at cost, measured over one quarter of 90 days. The figures are an illustration, not a real shop's accounts.
| Category | Average stock at cost | Cost of goods sold | Gross profit | Margin | GMROI | Days of stock |
|---|---|---|---|---|---|---|
| Drinks | ₦1,200,000 | ₦4,800,000 | ₦960,000 | 16.7% | 0.80 | 22.5 |
| Provisions | ₦3,000,000 | ₦6,000,000 | ₦900,000 | 13.0% | 0.30 | 45 |
| Toiletries | ₦1,500,000 | ₦1,500,000 | ₦450,000 | 23.1% | 0.30 | 90 |
| Household | ₦1,800,000 | ₦600,000 | ₦240,000 | 28.6% | 0.13 | 270 |
| Whole shop | ₦7,500,000 | ₦12,900,000 | ₦2,550,000 | 16.5% | 0.34 | 52 |
Household goods have the best margin in the shop, 28.6%, and the worst return on stock, 0.13. Their ₦1,800,000 sits for 270 days before it sells.
Drinks have one of the thinnest margins and the best return, 0.80, because the stock sells through every 22.5 days. Household holds 24% of the stock money and earns 9% of the gross profit. Drinks hold 16% and earn 38%.
Margin tells you what one sale earns. GMROI tells you what the money on the shelf earns, which is the number a small shop with limited cash should optimize.
The cash move this suggests
Move ₦600,000 out of household goods and into drinks. At drinks' current return of 0.80, it earns about ₦480,000 of gross profit a quarter. At household's 0.13, the same money earned about ₦80,000, so the shop gains about ₦400,000.
The move works on one condition: drinks must be running out today. Extra stock of a product that never runs out sells no faster, and earns nothing extra.
What should you do with each kind of category?
Sort each category by two questions: does its stock earn well, and does it run out? Each answer pair has a different fix.
| Category | What to do |
|---|---|
| High GMROI, runs out | Raise its reorder point and order-up-to level |
| High GMROI, never runs out | Leave it alone |
| Low GMROI, slow (many days of stock) | Cut the range, stop reordering slow lines, clear dead stock |
| Low GMROI, fast (few days of stock) | Fix the price or the supplier terms, not the quantity |
In the Ibadan example, household goods are low and slow, and provisions are low and fast. Provisions turn every 45 days on a 13% margin, so a better supplier price helps more than a smaller order.
Which inventory optimization levers come first?
Pull them in this order: each one frees cash or data the next one uses.
- Clear dead stock. It is cash you can release this month. Dead stock covers how to find and sell it.
- Rank products by what they earn. Find the small group of products that carries most of your profit. The 80/20 rule in inventory shows how to rank them with ABC analysis.
- Set reorder points and safety stock by rank. Top-ranked products get a bigger buffer. How to avoid overstocking and stockouts gives the formulas with a worked example.
- Plan for seasons. School terms, festive weeks and harvests move demand. Inventory forecasting methods turns last year's sales into this year's targets.
- Balance stock between branches. One branch's dead stock can be another's best seller. Seeing every branch from one place needs a shared system: cloud vs on-premises inventory compares the two kinds.
Inventory optimization strategies for retail lists more levers, for when these five are in place.
What inventory optimization is not, for a small shop
It is not buying forecasting software first. Forecasting tools learn from past sales, so they are only as good as the records you already keep.
It is not just-in-time buying either, which keeps almost no buffer. The Corporate Finance Institute notes the cost: there is rarely "any extra stock on hand to fill unexpected orders". A shop whose deliveries can run late needs a buffer.
The scorecard above needs no new software. It needs a quarter of honest sales and stock records, and one afternoon with a spreadsheet.
How to build the scorecard in ArmPOS
ArmPOS holds every figure the scorecard needs. Export each report to Excel and add up by category.
- Stock at cost: the Inventory Valuation report gives each product's stock on hand times its cost. Stock Inventory Valuation adds units sold and potential profit for a period (Stock reports).
- Gross profit: the Products report totals each product's sales for a period; if it shows nothing, use the Product sales report. Units sold times cost gives the cost of goods sold. Profit and Loss checks the total for the shop or one warehouse (Reports to check every day).
- Slow stock: the Dead Stock report lists products with no movement in 30, 60 or 90 days. Stock Aging sorts what you hold by how long ago it came in.
- What runs out: Product Quantity Alerts lists each product at or below its Stock Alert, by warehouse.
- The cash move between branches: a transfer moves stock from one warehouse to another once it is approved (Move stock between warehouses).
The reports work the same in every country: see ArmPOS in Nigeria and ArmPOS in South Africa.
Frequently asked questions
What is the main goal of inventory optimization?
To hold the least stock that still meets demand, so cash isn't stuck on shelves and best sellers don't run out. In practice, it means each naira of stock earns as much gross profit as it can.
What is a good GMROI?
There is no single good number across trades. Compare your categories with each other, and compare each with its own last quarter.
How often should a small shop review its inventory?
Build the scorecard every quarter, and check the low-stock list every day. Move cash between categories at the quarterly review, not on a busy Saturday.
What is multi-echelon inventory optimization?
It sets stock levels across a whole network at once, such as a central warehouse and its branches. Multi-echelon inventory optimization explains when a growing chain needs it.
Export last quarter's sales and stock, and fill in the scorecard for your own categories. To pull those figures from your till's own records, create a free ArmPOS account.
