Kanban Quantity Calculator

Each card represents one container's worth of replenishment, so a bigger container covers more units per card -- the same total buffer of units can be circulated with fewer, larger containers instead of more, smaller ones. This is why Container Size moves Kanban Cards Needed in the opposite direction from the other three inputs: raising it lowers the card count, while raising demand, lead time, or safety stock all raise it.

A longer lead time means more days pass between when a container is emptied and when its replacement arrives, so more containers -- and therefore more cards -- need to be in the pipeline simultaneously to keep the line supplied without a stockout. Lead Time enters the sizing formula as a direct multiplier alongside daily demand, so doubling it roughly doubles the required card count for a fixed container size and safety margin.

A 0% safety stock is a legitimate "no buffer" pull system: the calculator uses the (1 + S) multiplier directly, so at S=0 it simply computes cards from raw demand and lead time with no extra margin, rather than substituting some fallback default. This models a lean system that assumes perfectly steady, predictable demand -- any real variability in daily orders would risk a stockout under this setting.

Yes -- Days of Supply converts the calculated buffer inventory into how many days of average demand it covers, which is the same unit most reorder-point and safety-stock planning methods use, making it a reasonable apples-to-apples comparison point. It's driven almost entirely by Lead Time and Safety Stock, though: Days of Supply works out to roughly Lead Time x (1 + Safety Stock), since Daily Demand and Container Size largely cancel out of the ratio -- doubling Daily Demand or Container Size on its own leaves Days of Supply essentially unchanged, because both the buffer inventory and the demand it's measured against scale together. Doubling Lead Time, by contrast, roughly doubles Days of Supply.