What it means
A SKU sits one level below a product. A jacket is a product; the navy jacket in size medium is a SKU, with its own code, its own stock count and its own sales history.
SKUs matter because almost every operational number a retailer or manufacturer relies on is calculated at SKU level. Reorder points, stock cover, markdowns and demand forecasts all break down if two genuinely different physical items share a single code.
The count grows quickly, because SKUs multiply rather than add. Three styles offered in five sizes and four colours produce sixty separate codes, each needing its own shelf space, its own forecast and its own safety stock.
That multiplication is why SKU rationalisation is a standard cost exercise. Sales are usually concentrated in a small share of codes, so trimming the long tail frees warehouse space and working capital with little revenue lost, provided the lines being cut are not the ones drawing customers in.
A SKU is internal and specific to one business, which is what distinguishes it from a barcode or a manufacturer part number shared across the market. Two retailers can sell the same physical item under completely different SKU codes without any conflict at all.
In practice
Real-world examples
Example 1
A grocery chain lists a soft drink in three can sizes and two flavours, creating six SKUs from what shoppers see as one product. When the 330ml lime version keeps selling out, the buyer can only spot it because that variant has its own code and its own sales history.
Example 2
An electronics distributor discovers that two suppliers' identical cables were set up under one SKU. Stock counts never reconciled, and after splitting them into two codes the warehouse found $18,000 of unexplained shrinkage was actually a mislabelled receipt.
Example 3
A furniture retailer reviews 4,200 SKUs and finds 1,600 of them sold fewer than five units in a year. Discontinuing them cuts working capital by $340,000 and shortens the weekly replenishment run by two hours, with a revenue loss of under 3%.
Think of it
Think of an SKU like a fingerprint for a product. Just as no two people have the exact same fingerprint, no two products share the same SKU, making identification foolproof.
Formula
Calculation
Number of SKUs = Variant Option 1 x Variant Option 2 x Variant Option 3
Inventory Investment = Number of SKUs x Average Units Held per SKU x Cost per Unit
An outdoor clothing brand sells 3 jacket styles, each offered in 5 sizes and 4 colours. That gives 3 x 5 x 4 = 60 SKUs.
It holds an average of 40 units of each SKU at a cost of $12.00 a unit, so the inventory investment is 60 x 40 x $12.00 = $28,800.
The range generates $600,000 of annual revenue, and sales are heavily concentrated. The top 12 SKUs, which is 20% of the range, produce 80% of revenue, or $480,000. The remaining 48 SKUs share $600,000 - $480,000 = $120,000, an average of $120,000 / 48 = $2,500 each.
Dropping the weakest 20 of those slow sellers would release 20 x 40 x $12.00 = $9,600 of tied-up stock and remove roughly 20 x $2,500 = $50,000 of revenue. The decision turns on whether the freed cash, shelf space and forecasting effort are worth more than the margin on that $50,000.Case study
Seen in the real world
The following is an illustrative and entirely fictional example. Tidewater Home Goods, an invented homeware retailer, grew its range from 900 to 5,600 SKUs over four years as buyers added colours and sizes to chase every possible sale.
Revenue rose 22% across that period, but inventory rose 71% and the fictional company's stock turn fell from 5.1 times a year to 2.4. Warehouse pickers were walking further, forecast accuracy dropped because most codes sold in ones and twos, and a growing pile of stock had to be marked down each season.
A rationalisation review ranked every SKU by contribution and by whether it was ever bought alongside a bestseller. Tidewater cut 2,300 codes, released $2,100,000 of working capital and lost about $640,000 of annual revenue, most of it at low margin. Stock turn recovered to 3.9 within a year, and the buying team adopted a rule that a new SKU could only be added if an existing one was retired.
Watch out
Common mistakes
- Setting up one SKU for items that differ in size, colour or supplier, which makes stock counts, forecasts and reorder points unreliable.
- Adding SKUs to chase every possible sale without measuring what each one costs in working capital, warehouse space and forecasting effort.
- Cutting slow-moving SKUs on revenue alone, when some low-volume lines exist to complete a range and draw customers to the profitable items.
Questions
People also ask
What is the difference between a SKU and a barcode?
A SKU is an internal code a business chooses for itself, while a barcode such as a manufacturer product number is a shared identifier that is the same for every seller of that item.
How many SKUs should a business carry?
There is no correct number, but the useful test is whether each additional SKU earns more contribution than the inventory, space and complexity it consumes.
Do services need SKUs?
They often do, because giving each service package or support tier its own code lets a business track revenue, margin and demand in exactly the same way as physical stock.