Decision rule: calculate each SKU trigger from measured lead-time demand and an approved risk buffer, then review the setting when demand, suppliers, expiry risk or working-capital constraints change.
Turn the guide into a working forecast
Calculate a practical inventory reorder point using daily demand, supplier lead time and safety stock, while protecting cash and reducing stock-outs.
Open the Inventory Calculator and Tracker →The core reorder point formula
The basic formula is: reorder point = average demand during lead time + safety stock. Multiply the item’s measured demand rate by its measured replenishment lead time, then add the approved buffer. Place the order when usable stock reaches that documented trigger.
The formula is simple. Reliable inputs are not. Demand can change around payday, school terms, harvest periods, holidays and promotions. Lead time can change with ports, border clearance, production, transport, fuel shortages and supplier credit.
Measure usable stock, not shelf count alone
Usable stock is on-hand quantity minus damaged, expired, reserved, returned or quality-held items. Add confirmed inbound stock only when its delivery date and quantity are dependable. A purchase order is not available stock.
Use a SKU or product variant as the unit of control. Different sizes, colours, strengths or pack formats can have different demand and should not be mixed merely because the products share a name.
Calculate demand at the right level
Use recent issue or sales history, excluding cancelled orders and one-off data errors. A daily average is useful for fast-moving goods; a weekly average may be better for lower-volume stock. Compare the average with peak demand and note predictable seasons.
Do not let stock-outs lower the apparent demand. If the item was unavailable for seven days, recorded sales during those days do not show what customers wanted. Use lost-order notes, customer requests or comparable periods to adjust cautiously.
Measure supplier lead time honestly
Lead time runs from the point an order can actually be placed to the point stock is checked and available for sale. It can include approval, supplier preparation, international freight, customs, local delivery and receiving inspection. Measure actual order history, not only the supplier’s best estimate.
Separate normal lead time from worst credible lead time. Imported, regulated or custom-made goods need more protection than locally replenished standard goods.
Set safety stock by risk
Safety stock covers variation, not poor records. A simple approach is to compare peak demand during a slower delivery period with normal demand during normal lead time. Higher service-criticality, greater lead-time volatility and higher lost-sale consequences justify more protection.
Perishable, fashion and technology stock need restraint because excess stock can expire or lose value. Safety stock should be reviewed by product class rather than copied across the whole catalogue.
Connect reorder quantity to cash
The reorder point answers when to order. The reorder quantity answers how much. Before confirming a purchase, compare minimum order quantity, transport tiers, storage space, expiry, supplier discount, available cash and expected sales. A discount is not a saving if it creates dead stock or forces the business to miss payroll.
Use the cash-flow forecast to place deposits, balance payments, freight, duty and delivery in the periods when money will leave. For foreign-currency purchases, keep price and exchange assumptions visible.
Segment inventory instead of treating every SKU equally
Use an ABC-style review. High-value or high-impact A items need frequent counts and tight reorder settings. B items receive regular control. Low-value C items can use simpler replenishment, provided they are not operationally critical.
Add a second lens for criticality. A low-cost seal, cable or ingredient can stop an entire repair or production job. Value alone does not define business importance.
Create clean stock-control routines
- Record receipts, sales, returns, damage and adjustments promptly.
- Cycle-count high-value and fast-moving products more frequently.
- Use consistent units of measure for packs, pieces, litres or kilograms.
- Review slow and non-moving stock before placing new orders.
- Track supplier lead-time performance by order.
- Require a note and approval for manual stock adjustments.
Accounting and operational boundaries
IFRS Foundation, IAS 2 Inventories. IAS 2 addresses inventory cost, cost formulas and measurement at the lower of cost and net realisable value. A reorder model is an operational control, not a substitute for accounting policy, physical counts, expiry rules, tax treatment or regulated-product requirements.
How to test variable demand and delivery
Calculate one trigger with the item’s normal demand and lead time, then calculate a stress case with measured peak demand and delayed delivery history. The gap between those results indicates exposure; it is not an automatic instruction to hold that entire quantity as extra stock.
Review the item’s margin, value, criticality and shelf risk. A business may hold more protection for an essential low-cost part and less for an expensive slow-moving part, then use an expedited supplier option as a contingency.
Receiving controls protect the record
Count deliveries before updating available stock. Match the supplier document to purchase order, quantity, unit, batch, condition and expiry where relevant. Quarantine discrepancies instead of accepting them into sellable stock. Photograph or document damage according to supplier terms.
Record landed unit cost after the relevant freight and acquisition costs are known. Otherwise the quantity record may be accurate while pricing and margin decisions remain wrong. Keep accounting-cost policy separate from the operational trigger.
Returns, expiry and shrinkage
Returns should move through a defined status: resellable, repairable, supplier return, damaged or write-off review. Expiry-controlled products need batch and date visibility, with first-expire-first-out routines where appropriate. Shrinkage should be investigated by item, location and period rather than absorbed into a general adjustment.
When actual usable quantity repeatedly differs from the system, increasing safety stock hides the problem. Improve access control, counting, receiving and transaction capture first.
Metrics worth tracking
- Stock-out rate and lost-order notes.
- Inventory days or weeks by product group.
- Supplier lead-time average and variability.
- Forecast demand versus actual demand.
- Slow-moving and non-moving stock value.
- Expiry, damage, return and shrinkage value.
- Purchase commitments due before expected sales receipts.
A 30-day implementation plan
In week one, clean the SKU list and units. In week two, count the highest-value products and reconcile the tracker. In week three, calculate demand and actual lead time for the top sellers. In week four, approve reorder points, safety-stock logic and a weekly review routine.
Do not attempt perfect settings for every item at once. Start with the products that matter most to cash, customer service and operations. Record the initial assumptions and schedule a review after enough new sales and delivery evidence has accumulated.
Frequently asked questions
What is the reorder point formula?
Average demand during supplier lead time plus safety stock.
Is reorder point the same as reorder quantity?
No. The reorder point tells you when to order; the reorder quantity tells you how much to buy.
How do I account for supplier delays?
Use measured lead-time history and a safety-stock rule that reflects credible variation.
Can a small shop manage reorder points without expensive software?
Yes. Start with a controlled SKU list, regular counts and a simple tracker, then improve the inputs over time.