Two Problems, One Root Cause
Anyone who has run a warehouse knows the scene. Shelves are full of goods that have not moved in months, and on the same day a sales rep calls to say a key customer ordered an item you do not have. It looks contradictory: how can you be overstocked and short at the same time? The answer is that overstocking and understocking are not separate problems. They are two results of one failure: buying decisions that are not based on actual demand for each item.
When purchasing runs on habit or gut feel, stock builds up in the items the buyer is comfortable with or the supplier is discounting, while items whose demand has shifted quietly run low. The cash frozen in slow stock is exactly the cash that should have bought the missing items.
This guide puts numbers on the cost of each problem, lists the early warning signs, and then works through the practical tools for finding balance: days of cover, reorder points, safety stock, ABC analysis, forecasting and min-max levels, each with hypothetical worked examples.
What Overstocking Really Costs
Frozen working capital
Every item on the shelf is money paid out and not yet recovered. If you hold SAR 600,000 more stock than you need, that is money that could have repaid a bank facility, funded growth or captured early-payment discounts from suppliers. For businesses that run on short-term financing, excess stock turns directly into interest expense.
Carrying cost
Warehouses are not free. Rent, power and air conditioning (a real line item in the Saudi climate, especially for heat-sensitive goods), insurance, labour and safety systems all add up. Many companies estimate annual carrying cost as a percentage of inventory value, and the figure varies with the business, the materials and the cost of financing. Work out your own by adding up annual inventory-related costs and dividing by average inventory value.
Obsolescence and spoilage
Food and medicines expire, electronics are superseded, fashion goes out of season, and spare parts outlive the machines they served. On the accounting side, IAS 2 requires inventory to be measured at the lower of cost and net realisable value. When slow stock is worth less than it cost, you write it down and take the loss. Obsolescence is not a deferred problem; it lands in profit.
Forced markdowns
When stock piles up, discounting becomes the only way to free space and cash. Every unplanned markdown eats margin and teaches customers to wait for the sale rather than buy at full price.
Hidden operating costs
A crowded warehouse is slower to pick, more prone to handling damage and errors, and harder to count. Slow items sometimes occupy the prime locations near dispatch, pushing fast movers further away.
What Understocking Really Costs
Lost sales
A customer who cannot find the item buys it elsewhere. In retail that may be one receipt; in B2B it can be a whole supply contract. Worse, lost sales are not recorded anywhere, so management never sees their true size.
Damaged trust
"Currently unavailable" shakes a customer's confidence, especially a business customer planning around your delivery commitment. Repeat it often enough and they add a second supplier, then shift more volume to them.
Expensive emergency buying
Running out means express freight, buying from an alternative supplier at a higher price, or ordering small quantities without a discount. All of it is direct extra cost.
Stopped production and projects
In manufacturing, one missing material can halt a whole line. In contracting, a late material can delay a project phase and trigger delay penalties. The cost of the shortage can be many times the value of the missing item.
Side-by-Side Comparison
| Area | Overstocking | Understocking |
|---|---|---|
| Cash effect | Money frozen on shelves | Emergency buying at higher prices |
| Profit effect | Carrying cost, obsolescence, markdowns | Lost sales, stoppages, penalties |
| Customer effect | Limited and indirect | Direct and sometimes permanent |
| Visible in reports? | Yes, in the inventory balance | Usually not, because lost sales are never booked |
| Typical cause | Gut-feel buying, volume discounts, optimistic forecasts | Stale reorder points, outdated lead times, inaccurate balances |
Early Warning Signs
Do not wait for the annual count to find out. These signals can be tracked monthly:
- Falling inventory turnover. Cost of sales divided by average inventory. A drop from one period to the next means stock is growing faster than sales.
- High days of cover on specific items. An item with 200 days of stock and a 20-day lead time is plainly overstocked.
- Items with no movement for 90 or 180 days. Review this list regularly before it becomes dead stock.
- Repeat urgent orders. If the same item is ordered urgently more than once a quarter, its reorder point is wrong.
- Backorders and partial shipments. The share of orders not filled completely from stock is a direct measure of shortage.
- Large count variances. If system balances do not match the shelf, every buying decision rests on a wrong number.
Practical Tools for Finding Balance
1. Days of cover
The simplest and clearest tool. Days of cover = current stock / average daily usage. A hypothetical example: an item with 3,000 units on hand selling 50 a day has 60 days of cover. If its lead time is 15 days and your policy caps cover at 45 days, you hold roughly 750 units too many. That one number tells you not to reorder this item now.
2. Reorder point
The stock level at which you order so the new delivery arrives before you run out. The basic formula: reorder point = (average daily usage x lead time in days) + safety stock.
Example: an item uses 40 units a day, has a 12-day lead time and 160 units of safety stock. Reorder point = 40 x 12 + 160 = 640 units. When the balance drops to 640, the purchase order goes out. The full method is in our guide to the inventory reorder point.
3. Safety stock
Safety stock is not an arbitrary cushion. It is a calculated quantity that covers swings in demand and supplier delays. The simplest method:
Safety stock = (maximum daily usage x maximum lead time) minus (average daily usage x average lead time).
Hypothetical example: maximum daily usage 55 units, maximum lead time 15 days, averages 40 units and 12 days. Safety stock = 825 minus 480 = 345 units. This method is conservative and can overstate the need for less important items. For large item lists, companies use statistical methods based on the standard deviation of demand and a target service level, which we explain in our article on safety stock.
4. ABC analysis
Not every item deserves the same attention. Rank items by annual consumption value:
- A items: a small number of items making up most of the consumption value. Weekly review, carefully calculated safety stock, ongoing forecast checks.
- B items: the middle group. Monthly review is usually enough.
- C items: many items with small value. Simplify with fixed reorder levels and quarterly review.
A common mistake is treating a critical, low-value item as a C item. A cheap spare part can stop a production line, so it needs special handling despite its value.
5. Demand forecasting
Buying on last month's sales alone ignores seasons and trends. A useful forecast considers sales in the same period of previous years, Ramadan and Eid dates (which move about eleven days earlier each Gregorian year), planned promotions, and customers gained or lost. The goal is not perfect accuracy but an estimate closer to reality than a guess.
6. Min-max levels
A reorder point tells you when to order, not how much. Min-max completes the picture. The minimum is the reorder point, the maximum is the highest balance you are willing to hold, and the order quantity is the gap between the maximum and current stock. In the example above, with a minimum of 640, a maximum of 1,800 and a current balance of 600, you order 1,200 units. Stock never falls below the safety level and never rises above a ceiling set by space and cash. It is easy for storekeepers to understand, and a system can apply it automatically and propose purchase orders. Review the levels at least quarterly, or whenever the supplier or season changes.
Worked Example: A Food Distributor Before Ramadan
Take a hypothetical distributor selling a packaged date product. Normal daily sales are 80 cartons, rising to about 250 a day in the three weeks before and during Ramadan. The factory lead time is 10 days.
| Decision | Traditional approach | Data-driven approach |
|---|---|---|
| Pre-season quantity | One large order based on last year plus a safety margin | Successive orders driven by actual weekly sales |
| In-season reorder point | Left at the normal level | Raised to 250 x 10 plus safety stock |
| After Eid | Large surplus cleared at a discount | Small surplus cleared within weeks |
In the traditional approach, the reorder point stayed at 80 x 10 = 800 cartons, which covers barely three days of seasonal sales, so a stockout before the next delivery is almost certain. Meanwhile the big pre-season order may leave a surplus after Eid. The fix is to raise the reorder point and safety stock for the season and bring them back down afterwards, which is hard to do by hand across hundreds of items.
Who Owns the Balance?
Much of the problem is organisational, not mathematical. Each department sees inventory from its own angle:
- Sales wants everything in stock, because a stockout costs commission and customers, so it tends to overstate forecasts.
- Purchasing is often measured on unit price, so it leans toward large discounted orders.
- Finance wants less stock to free cash and may push for blanket cuts without distinguishing between items.
- The warehouse wants space and order, and feels the congestion first.
The answer is a short regular meeting where these groups decide on shared numbers from the same system: days of cover, slow movers, unfilled orders and the forecast for the next two months. Measure purchasing on turnover and stockout rate as well as price.
Monthly Metrics to Track
| Metric | Formula | What a rise means |
|---|---|---|
| Inventory turnover | Cost of sales / average inventory at cost | Faster movement, less frozen cash |
| Days inventory | 365 / turnover | Cash sitting on shelves longer |
| Fill rate | Orders filled complete from stock / total orders | Better customer service |
| Slow-stock ratio | Value of items with no movement in 180 days / inventory value | Higher obsolescence and markdown risk |
A hypothetical example: annual cost of sales of SAR 24 million and average inventory of SAR 6 million give a turnover of 4 and about 91 days of inventory. Raising turnover to 5 on the same sales cuts average inventory to SAR 4.8 million, releasing SAR 1.2 million of cash.
What to Do With Excess Stock You Already Have
- Stop ordering. The first and easiest step. Any item well above your cover policy is frozen until the balance comes down.
- Move it between branches. One branch's surplus may be another's shortage. An internal transfer is cheaper than any markdown.
- Negotiate returns. Some suppliers accept returns of sound goods for a fee or swap them for other items.
- Bundle. Pair a slow item with a fast one in a joint offer instead of a straight discount.
- Clear before it ages. A small early discount beats a large late one or a write-off.
- Book the write-down. If net realisable value falls below cost, record it under IAS 2 instead of postponing it.
Common Mistakes That Break the Balance
- One reorder level for every branch, even though usage varies widely by location.
- Stale lead times. A supplier that used to deliver in a week now takes three, and the system still plans on one.
- Buying for the discount. A 5% discount on six months of stock can cost more than it saves in storage and financing.
- Ignoring reserved and returned stock. The visible balance includes goods reserved for orders or damaged and awaiting return, so availability looks higher than it is.
- Relying on one person's memory. When the experienced buyer is away, the knowledge of when to order each item goes with them.
How an ERP System Keeps Inventory in Balance
All of these tools depend on three things: accurate balances for every item at every location, reliable usage history, and up-to-date lead times. That data only exists when sales, purchasing, transfers and receipts run through one system. Then slow-mover reports, reorder alerts and days of cover come straight from the system instead of manual spreadsheets.
In Tranquil, the inventory management module connects central inventory, branches and multiple units of measure, and integrates with purchasing, sales and financial accounting. Custom reports for slow movers and days of cover can be built through our customisation services. Contact the Tranquil team to review your current stock position.
Frequently Asked Questions
What is the difference between overstock and dead stock?
Overstock is more of an item than you need, but the item still sells. Dead stock has stopped selling entirely, expired or become obsolete. Overstock left alone for too long can turn into dead stock.
How much safety stock should I hold?
There is no fixed percentage. It depends on demand variability, lead time variability, the service level you want and how critical the item is. Critical items justify more safety stock; low-impact items can carry less.
How do I know if I am overstocked?
Calculate days of cover for each item and compare it with the lead time. An item with cover many times its lead time and no season coming up is very likely overstocked. Also review everything with no movement in the last 90 days.
Is ordering small quantities more often always the answer?
No. Frequent orders raise ordering and freight costs, and suppliers may not offer good prices on small lots. The right quantity balances ordering cost against carrying cost.
How should I plan for seasons like Ramadan?
Raise reorder points and safety stock for seasonal items at least one lead time before the season starts, then return them to normal before the season ends so you are not left with surplus afterwards.