Just-in-Time inventory is a logistics strategy that delivers materials only when they are needed for production or customer orders. It matters because inventory sitting on shelves costs money, takes space, and can become damaged or obsolete. In a JIT system, warehouses, suppliers, trucks, scanners, and production lines must act like one coordinated system.
The goal is to reduce waste while keeping work moving without delays.
JIT depends on accurate demand forecasts, reliable suppliers, fast communication, and carefully timed deliveries. Barcode scans, inventory dashboards, and warehouse management systems help track each item as it moves from supplier to dock to production. Small buffers may still be used to protect against traffic, machine breakdowns, or sudden demand changes.
When the timing works, JIT can lower storage costs and expose problems in the supply chain quickly.
Key Facts
- Inventory holding cost = average inventory value × annual holding cost rate
- Lead time = order processing time + production time + transportation time + receiving time
- Reorder point = demand rate × lead time
- Safety stock protects against uncertainty in demand or delivery time, but JIT tries to keep it small.
- Takt time = available production time ÷ customer demand
- JIT works best when suppliers are reliable, data is accurate, and delivery schedules are synchronized with production.
Vocabulary
- Just-in-Time inventory
- A system that delivers materials close to the exact time they are needed instead of storing large amounts in advance.
- Lead time
- The total time between placing an order and having the materials ready to use.
- Reorder point
- The inventory level at which a new order should be placed to avoid running out before the next delivery arrives.
- Safety stock
- Extra inventory kept as a buffer against uncertain demand, late deliveries, or process disruptions.
- Takt time
- The pace at which products must be completed to match customer demand during the available work time.
Common Mistakes to Avoid
- Assuming JIT means zero inventory, because a practical JIT system often keeps small buffers to handle normal variation and prevent shutdowns.
- Ignoring lead time, because even a small delivery delay can stop production when inventory levels are intentionally low.
- Using inaccurate demand data, because JIT schedules depend on matching deliveries to real production needs rather than guesses.
- Reducing warehouse stock without improving supplier reliability, because lower inventory only works when suppliers, transportation, and receiving processes are dependable.
Practice Questions
- 1 A factory uses 240 bolts per day and the supplier lead time is 3 days. Using reorder point = demand rate × lead time, what is the reorder point if no safety stock is used?
- 2 A warehouse holds an average of $80,000 in inventory and has an annual holding cost rate of 18 percent. What is the annual inventory holding cost?
- 3 A production line switches from large weekly deliveries to smaller daily JIT deliveries. Explain one advantage and one risk of this change.