Should the buffer be a percentage or a fixed quantity?

A percentage scales with the bin, so it stays proportional when usage or refill frequency changes. A fixed quantity does not scale, and it hides the basis; convert it to its share of the base first.

What coverage should a bin hold?

At least the time between refills, plus the buffer. A bin that covers less than one interval cannot be refilled in time, and the line waits. The coverage row makes that check directly.

How do two-bin systems use this quantity?

Each bin holds one replenishment quantity. When a bin empties, its card or empty container signals a refill, and the second bin covers usage until that refill arrives.

Does a bigger bin reduce stockouts?

It can hide the cause. A bigger bin covers a late refill but raises floor inventory and can mask a slow replenishment loop. Fix frequency and lead time first, then size the buffer from the remaining variation.

Lean Manufacturing & Operations calculator

Kanban Bin Quantity Calculator

Size a kanban bin from average daily usage, how often it is refilled and a buffer allowance. The page shows the base quantity, the buffer it adds and how many days the filled bin covers.

What this calculator does

Bin quantity with its buffer and days of cover from average usage, replenishment frequency and a buffer allowance.

Formula used

Base bin quantity = average daily usage ÷ replenishments per day
Buffer quantity = base bin quantity × buffer allowance ÷ 100
Bin quantity with buffer = base bin quantity + buffer quantity
Days of coverage = bin quantity with buffer ÷ average daily usage

Inputs explained

Average Daily Usage: Mean units consumed from this bin per production day.
Replenishments per Day: Scheduled refills of the bin per production day.
Buffer Allowance: Extra share of the base quantity for demand swings.

How to use the result

Best suited to sizing two-bin fasteners, resizing bins after a delivery change, checking coverage before a stockout.
A bin sized on average usage still runs dry on the worst day; the buffer allowance is the only cover. Scheduled refills that slip without a signal erode the coverage the bin buys.

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

Should the buffer be a percentage or a fixed quantity? A percentage scales with the bin, so it stays proportional when usage or refill frequency changes. A fixed quantity does not scale, and it hides the basis; convert it to its share of the base first.
What coverage should a bin hold? At least the time between refills, plus the buffer. A bin that covers less than one interval cannot be refilled in time, and the line waits. The coverage row makes that check directly.
How do two-bin systems use this quantity? Each bin holds one replenishment quantity. When a bin empties, its card or empty container signals a refill, and the second bin covers usage until that refill arrives.
Does a bigger bin reduce stockouts? It can hide the cause. A bigger bin covers a late refill but raises floor inventory and can mask a slow replenishment loop. Fix frequency and lead time first, then size the buffer from the remaining variation.

Last reviewed 2026-10-01.