Spare parts reorder point calculator
When to reorder idlers, belt, lagging and other conveyor spares, from usage, lead time and safety stock.
Result
How it works
The reorder point is the stock level at which you place a new order, so that the replacement arrives before the last spare is used.
It covers average use during the supplier lead time plus a safety stock for variation in demand and delivery. The result is rounded up to whole units.
Formula
ROP = ceil(daily demand × lead time + safety stock)
| Symbol | Meaning | Unit |
|---|---|---|
| ROP | Reorder point | units |
| Daily demand | Average consumption | units/day |
| Lead time | Time from order to receipt | days |
| Safety stock | Buffer for variation and criticality | units |
Worked example
Inputs: Average daily demand = 0.5 units/day; Replenishment lead time = 30 days; Safety stock = 5 units.
- Use during lead time = 0.5 × 30 = 15 units
- ROP = 15 + 5 = 20 units
- When stock falls to this level, raise the purchase order.
Assumptions and limits
- Assumes stable average demand and lead time.
- Set safety stock from criticality (what a stoppage costs), demand variability, installed quantity and supplier reliability.
- For critical, slow-moving items (drive pulleys, gearboxes, long belts) a min–max or insurance-spare policy is usually more appropriate than a usage-based ROP.
Screening estimate, not a design approval. Verify measured inputs, current standards, manufacturer limits and site procedures before purchasing, cutting or installation. Isolate and lock out equipment before any hands-on measurement.
Questions
What safety stock should I use?
Base it on how critical the item is and how much demand and lead time vary. Critical items with long lead times need more.
Does this work for one-off critical spares?
Not well. Usage-based ROP suits consumables such as idlers and scrapers; hold critical insurance spares by risk assessment.
Source notes
- Standard reorder-point method used in inventory control.
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