# Kanban Card Size Calculator (Number of Kanbans and Container Quantity)

> Source: https://netray.co/tools/kanban-card-size-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Calculate how many kanban cards or bins a part needs from daily demand, replenishment lead time, container size and safety factor.

## Category

supply-chain

## Industry

Discrete Manufacturing

## Audience

- Lean practitioner
- Production planner
- Materials manager

## Tool

**Kind:** calculator

**Inputs:**

#### Average daily demand

**Key:** demand

**Type:** number

**Default:** 240

**Min:** 0

**Step:** 10

**Unit:** pcs/day

#### Replenishment lead time

**Key:** lead_time

**Type:** number

**Default:** 1.5

**Min:** 0

**Max:** 60

**Step:** 0.1

**Unit:** days

**Help:** Time from card release to material back at the point of use, including waiting and transport.

#### Safety factor

**Key:** safety

**Type:** slider

**Default:** 20

**Min:** 0

**Max:** 100

**Step:** 5

**Unit:** %

**Help:** Policy factor to cover variability. Keep it low and reduce it over time.

#### Container quantity

**Key:** container

**Type:** number

**Default:** 60

**Min:** 1

**Step:** 1

**Unit:** pcs

**Help:** Fixed quantity per container or card.

**Outputs:**

#### Pieces needed during lead time (with safety)

**Key:** need

**Expr:** demand * lead_time * (1 + safety / 100)

**Format:** number

#### Number of kanbans (unrounded)

**Key:** cards_raw

**Expr:** need / container

**Format:** decimal

#### Number of kanbans

**Key:** cards

**Expr:** ceil(need / container)

**Format:** integer

**Primary:** true

**Description:** Rounded up so the loop never starves.

#### Maximum inventory in the loop

**Key:** max_inv

**Expr:** cards * container

**Format:** integer

**Primary:** true

**Description:** The ceiling that cards enforce.

#### Days of cover at maximum

**Key:** days_cover

**Expr:** if(gt(demand, 0), cards * container / demand, 0)

**Format:** days

**Chart:**

#### Number of kanbans vs replenishment lead time

**Type:** line

**X:** lead_time

**From:** 0.5

**To:** 10

**Steps:** 20

**Series:**

- cards

**Disclaimer:** Classic formula: kanbans equal demand times lead time times (1 plus safety factor), divided by container quantity. Container size should also respect packaging, handling and ergonomics.

## Content

**Intro:** Kanban only works when the number of cards is right. Too few starve the line, too many bring back the inventory you were trying to remove. This calculator applies the classic formula, rounds up to whole cards and shows the maximum inventory and days of cover.

**Sections:**

#### How to use the calculator

**Body:** Enter the average daily demand for the part and the replenishment lead time, which covers everything from the empty card being released to full material arriving at the point of use. Choose a safety factor that reflects variability in demand and supply; twenty percent is a common starting point but not a rule. Enter the container quantity, chosen first for handling and packaging reasons. The tool returns the number of cards, maximum inventory and days of cover.

**Bullets:**

- Use realistic demand, such as average of the last 8 to 13 weeks
- Measure actual lead time including queues and transport
- Choose container size by handling and ergonomics first
- Review the card count quarterly when demand changes

#### The formula

**Body:** The number of kanbans equals demand per day times lead time in days times one plus the safety factor, divided by the container quantity, rounded up. The result is also the number of full containers that can exist in the loop at once, so maximum inventory equals cards times container quantity. In the sample, 240 pieces per day, a 1.5 day lead time and 20 percent safety give 432 pieces needed, which is eight containers of 60. The chart shows the cards required as the lead time rises, which is the strongest argument for shortening replenishment time.

#### Practical use and ERP notes

**Body:** Most ERPs can run kanban natively, including SAP PP kanban control cycles, Oracle kanban replenishment and Infor SyteLine or LN pull signals, but the count of cards still has to come from analysis like this. Put the result into the control cycle or supply area configuration and review it with the line. If the card count must change often, treat that as a signal that demand or lead time is unstable.

#### Common mistakes

**Body:** Setting the safety factor high to hide problems, using planned lead time rather than actual, choosing very large containers to cut moves and then wondering why inventory rises, and failing to remove cards when demand falls. Also remember that kanban suits stable, repetitive demand; for lumpy or low-volume items other methods such as min-max may suit better.

**Cta:** If you want kanban quantities recalculated regularly from ERP demand and lead time data, with approval before updates, we can help set that up.

**Faq:**

#### What is the kanban formula?

**Answer:** Number of kanbans equals daily demand times replenishment lead time times one plus the safety factor, divided by the container quantity, rounded up to a whole number.

#### How do I pick the container quantity?

**Answer:** Pick a quantity that suits handling, packaging and ergonomics, and that gives a reasonable number of cards. Very small containers create many moves; very large ones create inventory.

#### What safety factor should I use?

**Answer:** Start with what variation requires, often 10 to 30 percent, and reduce it as you stabilize demand and supply. A high factor hides problems that kanban is supposed to expose.

#### Does kanban work for low-volume parts?

**Answer:** Usually less well. For irregular or very low demand, a reorder point or make-to-order approach may be better. Kanban is strongest for stable, repetitive parts.

## Search terms

kanban card calculator, number of kanbans formula, kanban quantity calculator, kanban container size, kanban sizing excel, toyota kanban formula, two bin kanban calculator, kanban safety factor

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