Lean teams use JIT because excess inventory hides problems and ties up cash and space. Lowering inventory exposes issues like unreliable machines or long changeovers. JIT depends on stable processes, so it is usually paired with TPM, SMED and standard work.
Where it comes from
Just-in-time is one of the two pillars of the Toyota Production System. Taiichi Ohno developed it at Toyota, drawing partly on how supermarkets restock shelves as customers take goods.
At a glance
Push compared with pull
Swipe sideways to see the whole diagram.
How to apply Just-in-Time
- 1
Map the value stream
Draw the current flow of material and information. Mark where inventory piles up and where work is pushed by schedules.
- 2
Set the pace with takt time
Calculate takt time from customer demand. Use it to size the flow and spot steps that cannot keep up.
- 3
Create continuous flow where possible
Link process steps so work moves one piece or small batch at a time. Remove waiting and transport between steps.
- 4
Use pull where flow is not possible
Place supermarkets and kanban between steps that cannot be linked directly. Upstream steps replenish only what downstream has used.
- 5
Level the schedule
Use heijunka to smooth the mix and volume released to the line. A level schedule keeps pull signals steady.
- 6
Lower inventory and fix what appears
Reduce buffers step by step. Each problem that surfaces becomes a target for kaizen before the next reduction.
Worked example (illustrative)
A furniture plant builds frames in large weekly batches, so about 5 days of frames sit before upholstery. It adds a small supermarket of 4 frames per model and kanban cards, so frames are made only when upholstery pulls them. Frames waiting fall to about 1 day of demand. A recurring frame defect that used to surface days later, after a whole batch was built, is now caught within a day.
Common mistakes
- Cutting inventory before equipment and suppliers are reliable, which causes shortages.
- Pushing inventory onto suppliers and calling it JIT.
- Using pull signals without leveling demand, so upstream steps swing between idle and overloaded.
When Just-in-Time is not the right tool
Just-in-time leaves little buffer, so it is exposed to supply disruption. Where supply is unreliable or lead times are long, planned buffers may be the sensible choice.
It also needs stable processes. Frequent breakdowns or long changeovers make small batches hard to run.
JIT inventory
JIT inventory means holding only the materials needed for current demand and receiving them close to when they are used. Instead of large stocks bought on a forecast, materials are replenished in small quantities as they are consumed.
Low inventory frees cash and space, and it exposes problems that stock used to hide, such as unreliable suppliers or long changeovers. That is also the risk: without stable processes and suppliers, a JIT system stops when something goes wrong.
Push vs pull
In a push system, each step makes products according to a schedule and pushes them to the next step, whether or not that step is ready. In a pull system, each step makes only what the next step has used, signaled by kanban.
JIT relies on pull. The pull system page covers how to set one up, including supermarkets and FIFO lanes between steps.
JIT at Toyota
Just in time is one of the two pillars of the Toyota Production System; jidoka is the other. Kiichiro Toyoda used the phrase in the 1930s, and Taiichi Ohno built the working system of kanban and pull at Toyota after the war.
Ohno's book on the Toyota Production System describes how the way American supermarkets restocked shelves inspired parts of the pull system.
What needs to be in place first
Common prerequisites are reliable equipment through TPM, short changeovers through SMED and clear standard work.
Kanban then carries the pull signals, and heijunka levels the load.
| Item | Push (forecast-driven) | Pull (just-in-time) |
|---|---|---|
| What starts work | A schedule or forecast | Actual use downstream |
| Inventory | Builds where the schedule runs ahead | Held in small, controlled stores |
| Typical tools | MRP schedules | Kanban, supermarkets, heijunka |
Guides on this topic
- Kanban board examples: 15 boards from different settingsKanban board examples for factories, hospitals, offices, software, sales, support, portfolios, classrooms and homes, with columns, WIP limits and lessons.Read the guide
- WIP limits: why limiting work in progress makes teams fasterWhat WIP limits are, why limiting work in progress shortens lead time under Little's Law, how to set a first WIP limit and how to handle urgent work.Read the guide
- Value stream mapping symbols: the standard VSM icon setValue stream mapping symbols explained: what each VSM icon shows, when to draw it, how to read the timeline, and tips for mapping by hand or in software.Read the guide
- Free kanban software: options, limits and when to payFree kanban software options, from a whiteboard or spreadsheet to free app plans and open-source tools. See what each option limits and how to choose.Read the guide
Sources
Books and papers show their publication year. Web pages show the month we last checked them.
- 1.Taiichi Ohno, Toyota Production System: Beyond Large-Scale Production (Productivity Press, 1988)
- 2.Yasuhiro Monden, Toyota Production System: Practical Approach to Production Management (Industrial Engineering and Management Press, 1983)
- 3.Toyota Motor Corporation, Toyota Production System (global.toyota, checked October 2026)