How to Plan a Profitable Merchandise Assortment

Walk into any large retail store and you will see thousands of products neatly arranged across categories. Behind that organised display sits a careful planning exercise that decides exactly what to stock, how deep to stock it, and how much profit each rupee of inventory should generate. This exercise is called merchandise assortment planning, and it is one of the most important decisions a retailer makes. Get it right and shelves stay stocked with products customers actually want. Get it wrong and you are left with either empty shelves or dead stock that has to be cleared at a loss. This post breaks down assortment planning into a clear three-step process and explains the financial tools that hold it together.

What assortment planning really means 🔗

At its core, assortment planning is the process of trading off variety, assortment, and backup stock. An assortment plan is simply a list of what a retailer wants to carry within a particular merchandise category. It does not stand alone. It pulls together sales forecasting, an inventory turnover plan, and a Gross Margin Return on Inventory Investment (GMROI) plan to show the full composition of a single category. Assortment planning is about getting the right product to the right location, in the right quantity, at the right time, to generate the best possible return on inventory.

A merchandise category is the basic planning unit here. It is a group of items that customers see as substitutes for one another. For example, all the regular cooking oils in a supermarket form one category, because a shopper choosing one is effectively choosing instead of another. Planning happens category by category rather than item by item, which keeps the process manageable.

Variety, assortment, and backup stock 🔗

Three terms sit at the heart of every assortment decision, and they are easy to confuse:

Variety refers to the number of different categories a store carries. This is sometimes called the breadth of the merchandise. A general store with groceries, stationery, cosmetics, and kitchenware offers high variety.

Assortment refers to the number of items, or SKUs, within a single category. This is the depth. A shop that stocks one brand of toothpaste has shallow assortment, while one that stocks fifteen brands in different sizes and variants has deep assortment.

Backup stock, also called buffer or safety stock, is the extra inventory held to meet demand when sales run higher than expected or when a delivery is delayed. It protects product availability. The catch is that wider variety, deeper assortment, and larger backup stock all tie up more money in inventory. Every retailer therefore has to balance the appeal of choice against the cost of carrying it.

Why GMROI sits at the centre of the plan 🔗

Before looking at the three steps, it helps to understand the single metric that ties financial discipline to assortment decisions. That metric is GMROI, short for Gross Margin Return on Inventory Investment. It answers a deceptively simple question: for every rupee invested in inventory, how much gross margin does the retailer earn back?

GMROI is powerful because it combines two things that retailers usually look at separately. It blends the gross margin percentage, which tells you how profitable each sale is, with inventory turnover, which tells you how quickly stock sells. A product can have a thin margin yet still be highly profitable if it sells fast, and a high-margin product can be a poor performer if it sits on the shelf for months. GMROI captures both effects in one figure, which is why it is one of the most relied-upon indicators of retail health.

How to calculate GMROI 🔗

The formula is straightforward. GMROI is calculated by dividing the gross margin by the average inventory cost:

GMROI = Gross margin ÷ Average inventory cost

Here, gross margin is revenue minus the cost of goods sold, and average inventory cost is the typical value of inventory held over a period. Suppose a category generates a gross margin of ₹5,00,000 on an average inventory cost of ₹2,00,000. The GMROI works out to 2.5. In plain terms, every rupee invested in that inventory returns ₹2.50 in gross margin. A result above 1.0 means the retailer is selling inventory for more than it cost to acquire and hold, while a value below 1.0 signals a loss on that investment. Many retailers treat a GMROI of around 2 to 3 as a healthy benchmark, though what counts as good varies by product category and sector.

One useful property of GMROI is that it can be measured at any level. A retailer can calculate it for the entire business, for a single department, for a region, or for one product. This flexibility is what makes it a practical tool for deciding which categories deserve more investment and which should be trimmed.

Step one: Organise the buying process by categories 🔗

The first step is organisational rather than financial. Deciding what to purchase and in what quantity is strategically significant, and it becomes especially complex for multi-store retail chains. A single chain may deal with thousands of items sourced from hundreds of vendors, both within the country and from abroad. Without structure, this would descend into chaos.

The solution is to organise the entire buying process by categories. Merchandise is divided into clearly defined categories, and each one is managed by a dedicated team. This usually involves buyers, who select and negotiate for products, merchandise planners, who handle the numbers and stock plans, and vendors, who supply the goods. By breaking a sprawling catalogue into manageable units, a retailer can assign clear responsibility, track performance accurately, and avoid the confusion that comes from treating the store as one giant undifferentiated pool of products.

This category structure also mirrors how customers actually shop. People look for products within categories, so planning along the same lines keeps decisions aligned with real buying behaviour. For a large chain, this organisation is not a luxury but a basic requirement for keeping the buying process under control.

Step two: Set merchandise financial objectives 🔗

Once categories are organised, each one needs financial targets. This is the step where GMROI does its real work. Overall business objectives are broken down and assigned to specific categories, and GMROI is calculated against those targets to judge whether a category is pulling its weight.

Retailers use a combination of tools to build these merchandise plans. Alongside GMROI, they rely on inventory turnover and sales forecasting. The gross margin percentage combined with the inventory turnover rate creates a particularly useful management tool, because it forces a category to be evaluated on both profitability and speed of sale at the same time. GMROI can be calculated by department, location, and item, which lets planners pinpoint exactly where a category is performing well and where it is dragging.

Setting these objectives turns vague ambitions into concrete numbers. Instead of saying a category should simply “do well,” planners commit to a target margin and a target turnover, then hold the category accountable to the resulting GMROI. This discipline is what stops a retailer from over-investing in attractive but unprofitable lines.

Step three: Develop an assortment plan with sales forecasting 🔗

With categories organised and financial objectives set, the final step is to build the actual assortment plan. This is where the retailer decides the precise mix of items to carry, and it depends heavily on sales forecasting. Forecasting well is what separates a profitable assortment from one buried in markdowns.

Knowing your merchandise type 🔗

Before forecasting, a retailer must identify where each category sits in its lifecycle and what type of merchandise it represents. Most retailers carry a mix of four broad types, and each behaves differently:

Staple merchandise consists of basic, everyday items that are in steady demand all year, such as rice, salt, milk, and plain cotton shirts. Demand is stable and predictable, so forecasting is relatively easy and these items are usually managed through continuous replenishment.

Fashion merchandise has cyclical demand driven by changing tastes and trends. Trendy apparel and seasonal footwear fall here. These items have a short selling window and are difficult to forecast, which makes buying them as much an art as a science.

Seasonal merchandise sells heavily only during specific times of the year. Diwali diyas, Holi colours, rakhi sets, and winter woollens are clear examples, with demand spiking and then falling away sharply.

Fad merchandise generates very high sales for a short burst before fading quickly. A novelty toy or a sudden trending gadget illustrates the pattern. The risk is buying too deep into something that disappears within weeks.

Forecasting methods 🔗

Sales forecasts draw on three main inputs. The first is past sales volume, the most reliable guide for staple and repeating items. The second is published secondary data, such as industry reports and market studies, which helps when a retailer lacks its own history for a new line. The third is customer surveys, which capture preferences and intentions directly from shoppers. For staples, past sales alone often suffice. For fashion and fad items with little history, retailers frequently extrapolate from a comparable item from a previous year and lean more on secondary data and customer insight.

Defining the store type 🔗

The trade-offs made during assortment planning ultimately define what kind of store a retailer is running. Balancing variety, assortment, and product availability shapes the store’s identity:

A specialty store chooses deep assortment within a narrow range of categories. A dedicated footwear store carrying dozens of styles, sizes, and colours fits this model. A convenience store offers limited variety and shallow assortment but high availability of everyday essentials, prioritising quick, easy purchases. A general store spreads itself across wide variety, carrying many categories at moderate depth so shoppers can find a bit of everything under one roof. Each format reflects a deliberate choice about how to balance the three levers, and the assortment plan is the document that makes that choice concrete.

Taken together, these three steps turn a chaotic universe of products into a controlled, profitable system. Organising by category brings order, setting financial objectives brings discipline, and forecasting-driven assortment planning brings the plan to life on the shelf. The retailers who do this consistently are the ones who keep the right products in stock while protecting their margins.

What do you think? If you were planning the assortment for a mid-sized store in your city, would you lean towards deeper assortment in fewer categories or wider variety across many? And how would you balance the appeal of stocking trendy fad items against the risk of being left with unsold stock?

References

1. https://www.davinciretail.com/resources/what-is-assortment-planning/
2. https://www.shopify.com/blog/gmroi
3. https://en.wikipedia.org/wiki/Gross_margin_return_on_inventory_investment
4. https://study.com/academy/lesson/evaluating-retail-performance-roa-gmroi.html
5. https://www.cottonworks.com/wp-content/uploads/2017/11/Section_1-Part_1.pdf