Car Care Products Inventory Planning in New Zealand: Reorder Points and Cash

Forecast Demand From Your Own Sales

Start with a SKU-level history, not a category average. Count units from completed, delivered orders for each product and separate cancelled orders, returns and bundles where they distort the product count. For illustration only, if a shampoo SKU sold 12, 15 and 13 units in the last three completed months, its simple average is (12 + 15 + 13) ÷ 3 = 13.3 units per month.

Then test whether recent demand has changed. If the latest four weeks produced 18 units compared with 12 in the preceding four weeks, that is a 50% increase, but it is not proof that the next period will also sell 18. Record the change and investigate its cause: a promotion, new channel, price change or seasonal event may not repeat.

Stockouts need a separate flag. A month with five units sold while the SKU was unavailable for ten days understates observed demand; do not treat it as a normal low-sales month. Add supplier timing and delivery history as planning context, rather than presenting an unsupported market benchmark as demand. ORVX can show inventory position, dead stock and remaining stock value, while its revenue reporting uses delivered orders and excludes returned or cancelled orders from realized revenue.

• Use the simple average when demand is stable and the recorded availability is consistent.
• Use a recent-period comparison when sales are changing, but document the event behind the change.
• Flag stockout-affected periods instead of allowing unavailable days to lower the apparent SKU demand.

Choose the Measure That Triggers Action

Use the measure that matches the decision you need to make. A reorder point is the purchase trigger: when available stock plus confirmed incoming units reaches that level, review whether to place an order. For illustration only, if your trigger for a 500 ml car shampoo is 18 units and inventory falls to 17, the SKU needs a purchasing decision. This is the most direct measure for deciding when to review replenishment, using your supplier timing and expected demand as inputs rather than relying on a calendar reminder.

Safety stock is a buffer, not usually the purchase quantity or the complete control rule. It protects availability against variation in sales or supply, but it does not by itself tell you how much to buy. Min-max levels provide broader stock control: set a minimum level that prompts review and a maximum level that defines the target after replenishment. That approach is useful when controlling shelf space, cash tied up in stock and order quantities across a range of products. In practice, use the reorder point to trigger a purchase review, safety stock to define the risk buffer, and min-max levels to control the replenished inventory range. You can test the arithmetic with this inventory reorder calculator.

Adjust for Lead Time and Safety Stock

Treat lead time as the full period from placing a supplier order to having sellable stock: supplier processing, freight to New Zealand and receiving. If a shampoo sells 4 units a day and those stages take 3, 7 and 2 days, expected lead-time demand is 48 units. A reorder point based only on supplier dispatch time would understate the stock required.

Set safety stock from observed uncertainty, not a universal percentage. Review demand during comparable lead-time windows and record how much lead time varied. For illustration only, if lead-time demand has ranged from 40 to 62 units, a trigger near 62 protects against that observed upper range; the implied safety stock is 14 units above the 48-unit average. Reassess it when a supplier, freight method or sales pattern changes.

The average lead time is useful for cash planning, while a longer observed lead time is more appropriate when a stockout is costly or replenishment is unreliable. Keep the buffer separate from expected demand so you can see how much cash is held for uncertainty. Test the arithmetic in the inventory reorder calculator, then compare its assumptions with your supplier and receiving records.

Forecasting with your own sales

Use the simplest method your sales history can support. A three-month average is transparent and useful for stable items: 90 units sold over three completed months gives a baseline of 30 units per month. A weighted average gives greater influence to recent months, which suits products gaining or losing momentum. A same-month comparison is more relevant when demand follows a repeatable seasonal pattern, but it needs enough history to show that pattern rather than one unusual promotion.

Forecast the measure that matches the planning decision. Units help estimate how many bottles, cloths or kits may be needed; revenue helps assess the cash value of the coming period. Do not treat a sales forecast as a promise that a reorder, promotion or price change will produce that result. Review forecast error after each period and change the method when the history shows persistent bias.

ORVX forecasts a coming period’s revenue from your own completed months using arithmetic and publishes the backtested error of the method used. That lets you compare the forecast with actual store performance rather than relying on a generic New Zealand category estimate. It also keeps profitability visible: revenue alone may rise while product margin, advertising contribution or remaining stock value deteriorates. For a hands-on calculation, use the inventory reorder calculator.

Lead time and safety stock

Estimate lead time separately for each supplier and SKU, then compare the quoted time with your actual order history. A supplier’s stated 10 days may become 18 days once dispatch delays, freight and receiving are included. Use the longer, evidenced figure when a late delivery would cause a stockout. Recheck it after delays, port disruption or a change in shipping method.

Safety stock is a buffer for demand or supply variation; it is not extra stock based on optimism. A simple calculation is: average daily demand × lead-time days = lead-time demand. If a wheel cleaner sells 3 units a day and lead time is 14 days, lead-time demand is 42 units. Add 12 units of safety stock and the reorder point is 54 units. When inventory position, sellable stock plus reliable incoming stock, reaches 54, review the purchase decision.

A fixed unit buffer suits stable products. A days-of-cover buffer is easier to adjust when sales change, but can inflate stock for slow items. Compare both in the inventory reorder calculator, then account for cash tied up in excess stock and the cost of missing sales.