In Part 1 of this series, we talked about The GAP Analysis, calculating your Optimum Inventory Level (OIL), Memo Stock and your Action Plan.

To start part 2 of this series, we will next explain GMROI and how to calculate your OIL for each product Category.

Now that you understand how much inventory you need overall, i.e. across all categories, it is time to calculate the inventory requirements in each category.

In order to understand how this works, you first need to understand GMROI.

GMROI is a formula whereby Mark-up multiplied by Stock-turn equals GMROI.  For example, if your mark-up is 100% (which is a 50% gross margin) and your stock-turn is 0.8 then your GMROI is 80 (100 x 0.8).  

What this means in real terms is that for every $100 you have invested in inventory, you are generating $80 of gross profit per annum.  

Here are some examples of how GMROI works in other retail sectors.

Retail Sector Stock-turn x Mark-up % = GMROI
Music 5 x 30 = 150
Clothing 2 x 100 = 200
Groceries 12 x 14 = 168
Jewelry 1 x 110 = 110


Important: I am not recommending the Jewelry figures above … they are however typical of what we see when making these sorts of comparisons.

As you can see, it is the combination of both stock-turn and mark-up that is important.  Groceries have by far the best stock-turn and Jewelry has the best mark-up, but overall, Clothing has the best GROI with $200 of gross profit from every $100 invested in inventory.

Here’s how GMROI works within a Jewelry store.

Category Stock-turn x Mark-up % = GROI
Diamond Rings 0.5 x 90 = 45
Gold Chain 0.7 x 145 = 105
Watches 1.4 x 70 = 97
Silver Jewelry 1.1 x 150 = 165


Important: Again, these are not recommended figures, nor are we suggesting you throw out your Diamond Rings and replace them with Silver because we also need to consider your Return on Effort (ROE).

So, in practical terms, your GMROI is the only way to genuinely compare the performance of one category with another.  We often hear retailers complaining about mark-up and threatening to drop a product line that in reality has a better GMROI than other products with a higher mark-up.

So how does this help you calculate the OIL for an individual category?

Well, following our example of ‘GAP’ Sales of $1.2m, let’s say 10% of your sales are currently coming from Diamond Rings and you want this to increase to 12% this year.  12% of $1.2m equals $144,000 of Diamond Ring sales.

Let’s also say that you intend to increase your mark-up on Diamond Rings to 100% and achieve a stock-turn of 0.8 (meaning on average you expect them to take 15 months to sell).  The OIL calculation would look like this. (Please note we can quickly, easily and affordably help you set up a Sales and Inventory Plan if required.)

Optimum Inventory All Categories Diamond Rings
Sales Budget (based on 12% of total) $1.2m $144,000
Budgeted Mark-up % 112% 100%
Budgeted Gross Profit (GP) $633,963 $72,000
Budgeted Cost of Sales (COS) (Sales less GP) $566,037 $72,000
Budgeted Stock-turn 1.2 0.8
Budgeted Inventory (COS ÷ by Stock-turn) $471,698 $90,000
Current Inventory $591,000 $77,000


So as you can see, in this example you would have $13,000 to invest in Diamond Rings … but alas there is a little more to it than that because you are already arguably over stocked by $119,302 overall.  Remember, another way to look at that is that you have enough inventory to do almost $1.8m in sales, I’d prefer to see you grow into your sales potential rather than shrink your inventory and therefore restrict future growth.   

Action Steps:

  1. Decide what your business is going to look like in the next 12 months.  For example, decide which categories you are going to build and which ones you are going to reduce (if any).
  2. Take each Category and determine what GMROI you expect (remember this is a combination of your mark-up and stock-turn in each category)
  3. Using these figures, calculate your Optimum Inventory Level (OIL) in each Category.  Important: Do one at a time and start with the Categories that can make the greatest amount of difference in the shortest amount of time.
  4. If you are already over stocked in a Category, decide whether you will increase your sales budget to match your inventory or reduce your inventory.
  5. If you are under stocked in a Category, look at other Categories that may be over stocked and work out how you can redeploy the investment where it’s needed.
  6. Before rushing out and buying blindly, think carefully about the price points and margin you want to achieve, the image you want to create and the vendors you want to partner.

This concludes the full series of Determining your Optimum Inventory Level.  If you need help accomplishing any of these concepts for your store, please do not hesitate to reach out to The Edge Retail Academy.  The Edge Retail Academy is a highly effective jewelry industry consulting company that provides customized strategies for retailers and vendors to increase profits, optimize growth, reduce debt, create profitable inventory solutions, build effective teams and enhance brand loyalty and profitability. The Academy is committed to helping jewelry businesses improve their bottom line while reducing uncertainty and stress. Edge Retail Academy software and the unique talent pool of their business advisors provide real world knowledge and advice for guaranteed results, all on a “no-contract” basis.  877-569-8657, ext. 1,  or