Why does the card count round up instead of down?

Each card authorises a full container, so a partial container cannot circulate. Rounding down would leave the loop short by up to one container, and that shortfall lands inside the lead time.

Is the safety allowance the same as safety stock days?

No. Here it is a share of demand during lead time, so it grows and shrinks with the loop. Safety stock days are a fixed cover of usage, a different basis.

How often should I re-count the cards?

After any change in daily demand, lead time or container quantity, because each one moves the count. Also review after a stockout, since that is evidence the allowance was too small.

Can I use dollar value instead of units?

Not in this count, because each card must match one physical container. For a value limit, convert the card count at cost and compare that with the loop inventory budget.

Lean Manufacturing & Operations calculator

Kanban Card Count Calculator

Work out how many kanban cards a loop needs to cover demand while material is replenished, and the inventory those cards authorise. You need daily demand, replenishment lead time, a safety allowance and the container quantity.

What this calculator does

Whole kanban cards a replenishment loop needs, and the inventory they authorise, from demand, lead time, safety and container size.

Formula used

Demand during lead time = daily demand × replenishment lead time
Safety stock = demand during lead time × safety allowance ÷ 100
Cards required = CEILING((demand during lead time + safety stock) ÷ container quantity)
Total kanban inventory = cards required × container quantity

Inputs explained

Daily Demand: Average units consumed downstream per production day.
Replenishment Lead Time: Days from a card signal to material back on the line.
Safety Allowance: Buffer for demand swings, from the card count review.
Container Quantity: Standard pack quantity that one card authorises.

How to use the result

Best suited to sizing a two-bin hardware loop, resizing cards after a lead time cut, setting up a first pull loop.
A demand spike needs more than a percentage allowance; recheck the count after any demand or lead time change. Variable supplier lead time needs safety stock built from its own spread, not this flat allowance.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).

Common questions

Why does the card count round up instead of down? Each card authorises a full container, so a partial container cannot circulate. Rounding down would leave the loop short by up to one container, and that shortfall lands inside the lead time.
Is the safety allowance the same as safety stock days? No. Here it is a share of demand during lead time, so it grows and shrinks with the loop. Safety stock days are a fixed cover of usage, a different basis.
How often should I re-count the cards? After any change in daily demand, lead time or container quantity, because each one moves the count. Also review after a stockout, since that is evidence the allowance was too small.
Can I use dollar value instead of units? Not in this count, because each card must match one physical container. For a value limit, convert the card count at cost and compare that with the loop inventory budget.

Related guides

Last reviewed 2026-10-01.