Two Bin System an Introduction
The two-bin system tells us about the inventory management system. It helps to determine when the inventory will be replenished and how to go about it. For example, there are 2 bins in the production, when one bin gets empty it is returned to the inventory. For the first bin the order is placed and the second bin in the production must provide the requisite inventory till the first bin is filled with enough raw materials or semi-finished goods. To understand various methods used in Kanban take up the Kanban training at StarAgile.
This system is sometimes called Kanban and the technique is called the Just-In-Time method.
The Impact of two-bin system in inventory management are as follows,
- It provides the method or the techniques on when the bins should be replenished with the materials.
- When the first bin is empty the order is placed to replenish the first bin. Till then the second bin must be used for production.
- The bin cards are used to record the inventory of the system
- This method is used for low value or small items that can be easily purchased or stored in large quantities.
Key Benefits of the Two-Bin System
A well-run two-bin system gives operations teams a low-effort way to keep materials flowing without constant manual counting. Here's what organizations gain when they adopt it:
- Simple to operate — teams don't need software or barcode scanners to run a two-bin inventory system on the shop floor.
- Cuts down on paperwork — unlike ledger-based tracking, a two-bin inventory needs no ongoing recordkeeping to work.
- Reduces stockouts — the second bin acts as a built-in buffer, so production rarely stalls while waiting on a reorder.
- Lowers carrying costs — because only two containers per part stay in circulation, a 2-bin inventory system avoids the excess stock that ties up cash.
- Improves visibility — an empty bin is a visual signal anyone on the floor can act on, no reports required.
- Speeds up training — new staff can learn a two-bin system in minutes because the rule never changes: bin empty, reorder.
- Works across industries — from hospitals stocking gloves and syringes to factories replenishing fasteners, the same two bin inventory control logic applies everywhere.
Limitations of the Two-Bin System
- No inventory method is perfect, and the two-bin system has boundaries worth knowing before you roll it out.
- Best suited to small, low-value parts — high-value or bulky items usually need tighter, more calculated control than a basic kanban bin system can offer.
- Assumes stable demand — if usage suddenly spikes, the second bin may run out before the reorder arrives.
- Depends on accurate bin sizing — a 2 bin system that's sized on guesswork instead of real lead-time data will either run short or tie up unnecessary stock.
- Limited insight into trends — because there's no ongoing count, a kanban bin system alone won't flag slow shifts in consumption the way digital tracking would.
- Still manual by design — someone has to notice the empty bin and place the order; nothing here automates itself, so process discipline matters as much as the containers do.
Why 2 Bin System of Inventory
Today’s organizations face the tough task of maintaining the inventory. If the stock is less then that means the production will come to a standstill and there will be no sales. There is a problem of losing out to the competitors. On the other hand, if there is excess inventory there is a problem of theft, spoilage of damage, etc, and then there is a huge cost associated with the inventory and we will not be able to circulate the cost in other value-added activities.
The two bin method is the way out to solve the above-discussed problems that are to maintain the right level of inventory. Take up the Kanban training with Kanban management professional certification at StarAgile.
The 2 bin system in its simplest form is discussed below with the steps,
- The first bin is placed right ahead or top of the second bin.
- A card for reordering is placed right below the 2 bin.
- The items for production is taken from the first bin which is ahead or on top of the second bin
- The first bin is replaced with the second bin when the first bin runs out of stocks
- The first bin is restocked with the reorder card
- When the reorder stocks arrive it is used to fill the first bin and then the process will continue to repeat.
This type of system is used widely in many industries such as hospitals and manufacturing industry etc.
Good and bad about 2 Bin System
The 2 bin system seems an interesting and workable solution for inventory management however there are pros and cons for it. For example, it is assumed that the time taken to reach the bottom of the second bin is more than the arrival of the reordered stocks otherwise this system fails.
The objective of the second bin is to have enough stocks to continuously produce the output. That is why this system is used for small parts inventory and those that are needed for the low volumes. Also, it is used where the stocks reorder does not take much time for replenishment of the parts of the raw material.
Sometimes it is thought that putting more parts to the 2 bins will help solve the above-discussed problems. But actually, it is not. This way it only increases the reorder dates or delays the reordering of the stocks this is where the 2 bin system fails.
To work with 2 bin we must ensure that it is done for small parts, small or low volumes, and reorder time is less. We must remember the correct math to reorder the quantities for effectively use the 2 bin system of inventory management
Learn DevOps with Generative AI
How does a Two Bin System Work?
We need to discuss the 2 important strategies of maintaining and using the 2 bin system.
Economic Order Quantity (EOQ)
EOQ is the method of finding the best order quantity for the items when compared to the best price value. In this method, the inventory costs lean towards the high end along with the ordering costs. This is accommodated to avoid the risk of disrupting production. This is generally used where there are high-speed assembly lines and when there is a high demand period. It helps the management in the reordering of the materials by understanding the lead times and consumption rates.
Kanban System of Inventory Management Guidelines
- Here as discussed the 2 bins system is based on the visual signal to replacement of the bin.
- The concept is reordering the materials when the first bin is empty and uses the second bin in production.
- Then repeat the steps to fill the second bins and so on.
- The bin must be put enough quantity to produce and survive till the empty bin is replenished.
Typical tools and methods of Kanban are discussed in Kanban training online conducted by StarAgile.
The industries where the 2 bin Kanban system can be used are
- Automobile
- Home appliances
- Electronics
- Medical supplies
- Furniture
- Engineering equipment manufacturing
Advantages of Inventory 2 Bin System
- Helps in inventory management of simple products
- The stock replenishment is automated
- There is no risk of sudden shortages of materials
- It accommodates the sudden change in demand
- It helps in stocks management in the shop floor and warehouses
- There is enough time for reordering quantities till the second bin is empty
The limitations of the two-bin inventory system are as follows,
- Can be used for only small quantities
- Is used for low volumes
- There is some cost associated in this system when compared to other inventory management system
- Calculations of the reorder quantities are required
- The reorder and replenishment rates must be higher than the bin materials or parts quantity; otherwise, there is a disruption in the production.
There are 3 metrics to look for in the 2 bin system
- The first one is the Day Sale of Inventory that is the number of days before the inventory is empty. The DSI level must be as low as possible to ensure a continuous supply of stocks.
- Next is the Inventory Turnover Ratio that is the cost of goods sold to average inventory. This ratio needs to be higher to help organizations to produce goods at speedier rates
- Another metric in 2 bin system is the formula for inventory and production items
Kanban Cards - "C"
Size of the Kanban - "S"
The lead time to replenish the inventory - "L"
Daily demand of Particular Parts - "D"
Then for calculation, the formula is (C-1)*S = L*D
To learn more about the Kanban metrics go for the Kanban certification at StarAgile.
Also Read: Kanban Inventory Management
Implementing a Two-Bin System: 10 Practical Tips
- Start with a pilot — roll out the two-bin system on a handful of parts before expanding it across the warehouse.
- Calculate reserve quantity properly — use (daily usage × lead time) + safety stock, not a round number picked at random.
- Label bins clearly — mark each bin with the part name, reorder point, and supplier so anyone can act on it.
- Place bins where they're used — keep the working bin within arm's reach of the production line to avoid wasted motion.
- Keep the reorder card with the bin — a card in the empty bin is a faster trigger than reporting to another department.
- Review lead times regularly — a two-bin inventory system only works if the reserve stock actually outlasts the supplier's delivery time.
- Track exceptions — note the rare times a bin runs out early, since that data usually reveals a sizing error.
- Train the whole shift — everyone touching the bin should know the reorder rule, not just the shift supervisor.
- Reassess bin size after demand changes — a 2-bin inventory system set up for stable demand should be revisited if volumes shift.
- Combine with periodic audits — spot-check bin quantities occasionally to catch drift before it becomes a shortage.
Two-Bin System vs Single-Bin System
A single-bin system keeps one container of stock and relies on someone tracking the remaining quantity, then placing an order once it hits a set reorder point. It works, but it depends entirely on someone noticing the number before it's too late.
A two-bin system removes that dependency. Because the second bin is a physical reserve, the reorder trigger is visual rather than tracked — the team switches bins and knows exactly how much runway is left.
Aspect | Single-Bin System | Two-Bin System |
Reorder trigger | Manual count reaches reorder point | Bin runs empty |
Risk of stockout | Higher — depends on accurate counting | Lower — buffer stock is physically separate |
Setup effort | Simple, one container | Slightly more space, two containers |
Best for | Low-volume, easily monitored items | High-turnover, low-value parts |
For most shop floors managing a two-bin inventory, the extra container is a small trade-off for the drop in missed reorders.
Final Conclusion
Typically the 2 bin seems simple but its implementation and along with planning the Kanban system is challenging practically. To know more about Kanban register for the training and Kanban course at StarAgile. StarAgile offers KMP 1 certification to the professionals who want to take up a career in project management using Kanban.
FAQs
1. What is a 2 bin system?
A 2 bin system is an inventory method where two containers hold the same part — one in active use and one in reserve — so a reorder is triggered the moment the first bin runs empty.
2. What is the two-bin approach?
The two-bin approach is another name for the same method: it uses two containers per item so production keeps running from the reserve bin while the working bin is being replenished.
3. How do you calculate the 2 bin system?
The reserve bin quantity is generally calculated as (daily usage rate × lead time) + safety stock. This ensures the second bin holds enough stock to last until the reorder arrives.
4. What is a bin system?
A bin system is any inventory method that uses labeled containers to track and replenish stock visually, rather than through continuous counting. The two-bin inventory system is the most common version of this approach.
5. What is BIN full form?
In inventory contexts, BIN isn't an acronym — it simply refers to the storage container used to hold and track parts or materials.
6. What is the difference between Kanban and two-bin system?
Kanban is a broader pull-based signaling system that can use cards, boards, or bins to trigger replenishment. The two-bin inventory system is one specific way to apply Kanban principles, using two physical containers instead of cards or software.
