Skip to main content

Kanban Lot Size Q&A

Micro Lessons


What’s the formula for calculating Kanban lot size?


(Warning: There is no escaping the math!)
Calculating Kanban lot size is actually a secondary calculation. The number of kanban (or signals) required for an item to be held in the supermarket must first be calculated.

Yasuhiro Monden (author, and instrumental in introducing JIT Production System to the U.S.), expressed this first calculation as follows:

#KB = (ADD x (RF+LT+ST))/CQ

#KB = Number of Kanban; ADD = Average Daily Demand; RF= Run Frequency; LT = Lead Time; ST = Safety Time; CQ = Container Quantity

If we apply Monden’s equation to the original question, “What’s the formula for calculating Kanban lot size?,” the calculation flows as follows:

KBLS= Kanban Lot Size; KBRQ= Kanban Run Quantity; KBQ= Quantity of units each kanban (or signal) authorizes.

Keep in mind…
1. Continuous Flow, not Kanban, is the preferred way to connect processes.
2. In most cases, other value stream improvements (i.e., equipment uptime, reliability improvements and changeover reduction) will precede Kanban system implementation.

Have a question you’d like answered? Send it a long then watch for it to be answered in a Word of the Month post!