Kanban Card Quantity Calculator

Deterministic sizing for replenishment loops

Inputs

Demand and lead time must use the same time unit.

units
Average demand per selected time unit.
periods
Replenishment lead time in the same unit.
%
Use 20 for a 20% buffer.
units
Quantity represented by one card.
Cards = ceil((100 x 2 x (1 + 0.2)) / 50) = 5

Self-Tests

Golden tests from the build specification.

Not run
  • D 100/day, LT 2 days, safety 20%, container 50 -> 5 cards Pending
  • D 50, LT 3, safety 0%, container 25 -> 6 cards Pending
  • Fractional raw result always rounds up Pending

About the Kanban Card Quantity Calculator

Maintaining optimal inventory levels between manufacturing processes prevents both stockouts and excessive work-in-progress storage. Calculating the correct Kanban card quantity establishes a reliable pull system based on actual consumption rates, lead times, and required safety stock. Materials managers and supply chain planners rely on this formula to streamline factory floor logistics and improve cash flow.

How it works

  1. Determine the average daily demand for the specific part or subassembly.
  2. Enter the total replenishment lead time required to produce or order a new batch.
  3. Set a safety stock percentage to buffer against demand spikes or supply delays.
  4. Input the standard container capacity to generate the exact number of cards needed.

Frequently asked questions

What factors should I include in replenishment lead time?

Lead time must include processing time, setup time, waiting time, and the physical transportation time required to move the container from the supplier to the point of use.

How do I determine the right safety stock factor?

The safety factor usually ranges from 10% to 20%, depending on the historical variability of customer demand and the reliability of your supplier or upstream process.

Should I recalculate these values frequently?

Yes, parameters should be reviewed and adjusted periodically, especially if there are significant changes in customer demand, machine cycle times, or supplier lead times.

What happens if the formula results in a fraction?

You should always round up to the next whole number to ensure you have enough inventory to cover the system's calculated requirements and avoid starving the production line.

References