{ "slug": "kanban-card-count", "title": "Kanban Card Count Calculator", "heading": "Kanban Card / Bin Count Calculator", "category": "other", "url": "https://www.revenuelab.fyi/toolbox/kanban-card-count", "summary": "How many kanban cards or bins you need to run a pull system without stockouts.", "description": "A kanban system replenishes exactly what was consumed, and the number of cards (or bins) in the loop determines how much inventory circulates in that loop at any time — too few cards and you risk stockouts when replenishment lead time or demand spikes; too many and you're carrying unnecessary WIP that defeats the purpose of pull production. This calculator uses the standard kanban sizing formula: average daily demand times replenishment lead time (in days) gives the base pipeline quantity, then a safety factor is added to buffer against demand variability and supplier reliability, and the whole thing is divided by container/bin size to get the number of cards or bins needed. Lead time here should include the full loop — production or supplier lead time plus any queue, transport, and processing time before the container returns to the point of use, since kanban has to cover the complete replenishment cycle, not just production time.", "formula": "Cards Needed = ROUNDUP((Daily Demand × Lead Time in Days × (1 + Safety Factor)) ÷ Container Quantity).", "dateModified": "2026-09-30", "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=kanban-card-count", "inputs": [ { "id": "dailyDemand", "label": "Average daily demand", "kind": "number", "hint": null, "default": 240, "unit": "units", "min": 0, "max": null }, { "id": "leadTimeDays", "label": "Full replenishment lead time", "kind": "number", "hint": null, "default": 3, "unit": "days", "min": 0.1, "max": null }, { "id": "safetyFactor", "label": "Safety factor (buffer for variability)", "kind": "number", "hint": null, "default": 25, "unit": "%", "min": 0, "max": 200 }, { "id": "containerQty", "label": "Units per container/bin", "kind": "number", "hint": null, "default": 50, "unit": null, "min": 1, "max": null } ], "outputs": [ { "id": "cardsNeeded", "label": "Kanban cards / bins needed", "format": "number", "hint": null, "primary": true }, { "id": "totalUnitsInLoop", "label": "Total units circulating in the loop", "format": "number", "hint": null, "primary": false }, { "id": "daysOfCoverage", "label": "Days of demand coverage", "format": "decimal", "hint": null, "primary": false }, { "id": "pipelineQty", "label": "Exact pipeline quantity (before rounding)", "format": "decimal", "hint": null, "primary": false } ], "worked_example": { "inputs": [ "Average daily demand: 240 units", "Full replenishment lead time: 3 days", "Safety factor (buffer for variability): 25 %", "Units per container/bin: 50" ], "outputs": [ "Kanban cards / bins needed: 18", "Total units circulating in the loop: 900", "Days of demand coverage: 3.8", "Exact pipeline quantity (before rounding): 900" ] }, "how_to": { "title": "How to use this", "steps": [ "Enter average daily demand (units).", "Enter full replenishment lead time (days).", "Enter safety factor (buffer for variability) (%).", "Enter units per container/bin.", "Read your kanban cards / bins needed on the right — it updates as you type.", "Hit Share to keep the scenario or send it to someone." ] }, "scenarios": [ { "name": "Conservative", "description": "Lower-end numbers — what if things land soft?", "values": { "dailyDemand": 145, "leadTimeDays": 1.7999999999999998, "safetyFactor": 15, "containerQty": 30 } }, { "name": "Typical", "description": "Defaults — the most common real-world setup.", "values": { "dailyDemand": 240, "leadTimeDays": 3, "safetyFactor": 25, "containerQty": 50 } }, { "name": "Ambitious", "description": "Higher-end numbers — what if things really pop?", "values": { "dailyDemand": 385, "leadTimeDays": 4.800000000000001, "safetyFactor": 40, "containerQty": 80 } } ], "limitations": [ "Estimates assume standard, average conditions — local rules, pricing, and materials vary.", "Results are rounded for readability; add a buffer before ordering, booking, or committing.", "Double-check anything with a real cost attached against a local quote." ], "faq": [ { "q": "What safety factor should I use?", "a": "20-30% is a common starting point for stable, well-understood processes with reliable suppliers. Increase it toward 50-100% for volatile demand, unreliable supplier lead times, or a new kanban loop where you don't yet have confidence in the process — you can tighten it later once you have real performance data." }, { "q": "What lead time should I use if the supplier ships weekly?", "a": "Use the full cycle from when a card is triggered to when replenished stock is available and usable at the point of use — including any batching delay (average half the shipping cycle if orders are batched weekly), transit time, receiving/put-away time, and any incoming inspection. Underestimating lead time is the most common kanban sizing mistake." }, { "q": "How does container size affect card count?", "a": "Smaller containers require more cards to hold the same total pipeline quantity, but they also mean smaller replenishment triggers and tighter WIP control, which is usually preferred in lean systems. Very large containers reduce card count but can hide problems and slow response to demand changes — most lean practitioners favor smaller containers even though it means managing more cards." }, { "q": "Should I recalculate kanban sizing regularly?", "a": "Yes — review it whenever demand shifts materially or lead time changes (new supplier, process change), typically on a quarterly cadence at minimum. A kanban loop sized for last year's demand pattern will either starve the line or build excess WIP if conditions have changed." } ], "related": [ "https://www.revenuelab.fyi/toolbox/spare-parts-stocking", "https://www.revenuelab.fyi/toolbox/capacity-vs-shifts" ], "license": "CC-BY-4.0", "citation": "RevenueLab — Kanban Card Count Calculator (https://www.revenuelab.fyi/toolbox/kanban-card-count)" }