Lot-for-Lot — Manufacturing Glossary

Lot-for-lot is a lot sizing method in MRP that orders exactly the quantity needed for each planning period — no more, no less. Also called discrete ordering or LFL, lot-for-lot minimizes inventory carrying costs by producing or purchasing only what is required to meet net requirements in each time bucket.

At User Solutions we see lot-for-lot used most often in make-to-order job shops and for high-value components where the cost of holding excess inventory outweighs the savings from larger batch sizes.

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How Lot-for-Lot Works

When MRP calculates net requirements by period, the lot-sizing rule determines how to group those requirements into orders. Lot-for-lot takes the simplest approach:

1. MRP calculates net requirements for each period.
2. If net requirements are positive in a period, lot-for-lot generates a planned order for exactly that quantity.
3. No combining of requirements across periods.
4. Planned receipt equals planned need — ending inventory is zero.

This contrasts with methods like EOQ, which may order more than needed in one period to reduce ordering frequency.

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Lot-for-Lot Example

A manufacturer needs component X-50 over a 6-week horizon. MRP has calculated these net requirements:

Lot-for-lot generates planned orders matching each non-zero period:

Total ordered: 195 units across 4 orders.

Compare with EOQ of 100:

Total ordered: 300 units across 3 orders — 105 units of excess inventory at the end.

If component X-50 costs $200 each, lot-for-lot avoids carrying an average of $13,000 in unnecessary inventory. The trade-off is one additional order (and its associated setup or ordering cost).

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Why Lot-for-Lot Matters for Scheduling

Minimizes work-in-process inventory. For expensive manufactured components, lot-for-lot keeps WIP and finished component inventory near zero. Less capital is tied up on the shop floor.

Aligns production with actual demand. In make-to-order environments, lot-for-lot naturally matches production to customer orders. There is no overproduction and no risk of obsolete inventory.

Simplifies scheduling decisions. Each planned order maps directly to a specific demand. Scheduling tools like Resource Manager DB can trace every production job back to the customer order that requires it, making priority decisions clear.

Reduces waste from engineering changes. When products change frequently, holding excess inventory risks scrapping outdated components. Lot-for-lot eliminates this risk by ordering only what is immediately needed.

Increases setup frequency. The trade-off is real — more orders mean more setups. For items where setup time is significant relative to run time, this can reduce effective capacity. Planners must weigh setup costs against carrying costs.

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Related Terms

• Lot Sizing — The category of methods for determining order quantities, including lot-for-lot, EOQ, and fixed-period approaches.
• Economic Order Quantity (EOQ) — A lot-sizing method that balances ordering and carrying costs, often producing larger batches than lot-for-lot.
• Net Requirements — The calculated demand that lot-for-lot uses to set order quantities for each period.

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FAQ

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This term is part of the Manufacturing Glossary. For a deep dive into material planning, see our MRP Guide.