2 Bin System Result
Reserve Bin Quantity
0
Working Bin Quantity
0
Total Target Stock
0
Safety Stock
0
Suggested Order Quantity
0
Status
Ready
Advanced 2 Bin System Calculation
Enter usage, lead time, variation, service level, and ordering rules. The calculator estimates reserve stock, working stock, and the refill quantity.
Example Data Table
| Item | Daily Demand | Lead Time | Cycle Days | Pack Size | Reserve Bin | Working Bin |
|---|---|---|---|---|---|---|
| Gloves | 50 | 7 | 10 | 25 | 425 | 500 |
| Labels | 120 | 4 | 6 | 50 | 600 | 750 |
| Fasteners | 35 | 12 | 14 | 20 | 520 | 500 |
Formula Used
Lead Time Demand = Average Daily Demand × Lead Time Days
Safety Stock = Z × √((Lead Time × Daily Demand Deviation²) + (Average Daily Demand² × Lead Time Deviation²))
Reserve Bin = Lead Time Demand + Safety Stock
Working Bin = Average Daily Demand × Working Bin Cycle Days
Total Target Stock = Reserve Bin + Working Bin
Suggested Order Quantity = Total Target Stock − Current Stock
Pack size rounding is applied after each stock estimate. Minimum order quantity is also checked before showing the final order.
How to Use This Calculator
Enter the average number of units used each day.
Add supplier lead time in days.
Enter demand and lead time deviation for risk control.
Select the service level that matches your shortage tolerance.
Add pack size and minimum order quantity.
Enter current stock on hand.
Click calculate to see bin sizes and ordering advice.
Use the CSV or PDF buttons to save the result.
Complete Guide to 2 Bin System Calculation
What the 2 Bin System Means
A 2 bin system is a simple inventory control method. Stock is divided into two clear parts. The first bin supports daily use. The second bin acts as the reorder signal. When the first bin becomes empty, the second bin is opened. At the same time, a new order is placed. This keeps work moving while the supplier prepares the refill.
Why Accurate Bin Size Matters
The method looks simple, but the calculation needs care. If the reserve bin is too small, shortages may happen. If both bins are too large, cash stays locked in stock. Extra inventory can also increase storage cost. A good calculation balances service, cost, and risk. It also gives staff a clear visual control point.
Demand and Lead Time
Daily demand is the main driver. Lead time is also important. Higher demand needs larger bins. Longer lead time also needs more reserve stock. Demand deviation adds risk. Lead time deviation adds more uncertainty. The calculator uses both values to estimate safety stock.
Service Level and Safety Stock
Service level shows how strongly you want to avoid stockouts. A higher service level creates more safety stock. This is useful for critical items. A lower service level may suit cheap and easy items. The selected Z value changes the reserve amount. This gives more control than a fixed percentage method.
Practical Planning
Pack size and minimum order quantity affect real orders. Suppliers rarely ship exact calculated units. This tool rounds results to practical pack quantities. It also checks current stock. If stock is below the reserve bin, the result warns you. Use the output during purchasing, warehouse checks, and reorder planning. Review values often when demand changes.
Frequently Asked Questions
What is a 2 bin system?
A 2 bin system separates stock into working and reserve quantities. The working bin is used first. When it is empty, the reserve bin starts and a reorder is placed.
What does the reserve bin mean?
The reserve bin covers expected demand during supplier lead time. It also includes safety stock when demand or lead time is uncertain.
Why is safety stock included?
Safety stock protects against demand spikes, supplier delay, counting errors, and process variation. It lowers the chance of running out before the refill arrives.
What is the working bin?
The working bin supports regular use before the reorder point is reached. It is based on average daily demand and the selected working cycle days.
How is service level used?
Service level controls the Z value in the safety stock formula. A higher level increases protection but also raises inventory quantity.
Why does pack size change the result?
Many suppliers ship in cartons, boxes, or fixed packs. The calculator rounds stock quantities upward so the order matches practical purchasing rules.
When should I reorder?
You should reorder when the working bin is empty or when current stock falls at or below the reserve bin quantity.
Can this calculator handle critical items?
Yes. For critical items, select a higher service level and use realistic demand and lead time variation. This creates a stronger reserve quantity.