EOQ (Economic Order Quantity)

Indian factory storekeeper sorting spare parts by priority, representing VED inventory classification

TL;DR: Economic Order Quantity (EOQ) is the order size that minimizes the combined cost of ordering and holding inventory, calculated from annual demand, order cost, and holding cost per unit. The textbook formula assumes steady, predictable demand, which is exactly what makes it unreliable for most Indian manufacturing SMEs without adjustment.

Ordering too much ties up cash in stock sitting on a shelf. Ordering too little means more frequent orders and a higher chance of running short. EOQ is the formula built to find the middle.

What Is EOQ?

Economic Order Quantity is the order quantity that minimizes total inventory cost, the sum of ordering cost, what it costs to place and process an order, and holding cost, what it costs to store that inventory until it’s used.

The classic EOQ formula is the square root of (2 times annual demand times ordering cost) divided by holding cost per unit per year. As order size goes up, ordering cost per unit falls but holding cost rises, EOQ finds the quantity where the two curves cross.

EOQ was built for a world of stable demand and fixed lead times. It works cleanly for raw material with steady, predictable consumption; it breaks down fast for seasonal items, new products with no demand history, or vendors with inconsistent lead times.

Where EOQ Fits in Purchasing Decisions

How to Calculate EOQ

Working out EOQ comes down to three inputs and one formula:

Annual demand (D). Total units consumed over a year, based on actual historical usage, not a rough guess.
Ordering cost (S). The cost to place and process a single purchase order, admin time, follow-up, receiving effort, not just the item price.
Holding cost per unit (H). The annual cost to store one unit, covering warehousing, insurance, capital tied up, and shrinkage risk.
Apply the formula. EOQ equals the square root of (2 times D times S divided by H). A worked example: annual demand of 12,000 units, ordering cost of ₹500, holding cost of ₹20 per unit gives an EOQ of about 774 units per order.

Indian factory worker operating a digital touchscreen control panel on a machine

Where the EOQ Formula Breaks Down

The textbook formula assumes conditions that rarely hold in a real Indian manufacturing SME:

Assumes constant, predictable demand. Seasonal products or new SKUs with no usage history don’t have a reliable demand number to plug into the formula.
Assumes a fixed, reliable lead time. A vendor with inconsistent delivery dates makes any fixed order-size formula risky without a safety-stock buffer added on top.
Ignores quantity discounts. Many suppliers offer per-unit price breaks at higher order volumes that the basic formula doesn’t account for at all.
Treats holding cost as a flat, known number. Most SMEs don’t actually calculate their true holding cost, warehousing, capital, shrinkage, so the formula runs on a guessed input.
Used once and never recalculated. Demand, costs, and vendor terms all shift; an EOQ calculated a year ago is often quietly wrong today.

Do you know your real annual demand and holding cost per SKU, or is your order quantity still based on habit?

TranZact’s stock valuation and consumption history gives you the real demand and cost numbers EOQ needs, instead of a rough estimate from memory.

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EOQ vs Just-In-Time Ordering

Order size: EOQ calculates one fixed optimal quantity per order; JIT uses small, frequent orders sized to near-term need.
Assumption: EOQ assumes stable demand and lead time; JIT assumes reliable, fast vendor delivery so large buffer orders aren’t needed at all.
Cash impact: EOQ still ties up cash in a calculated buffer; JIT minimizes cash tied up by ordering closer to actual consumption.
Risk: EOQ is more forgiving of a single late delivery since it carries more stock per order; JIT is more exposed to vendor delays since buffer stock is minimal.
Manufacturer relevance: EOQ suits stable, high-volume raw material with reliable vendors; JIT suits high-value or fast-moving materials where vendor lead times are dependable. Most Indian SMEs run a hybrid of both.

How TranZact Supports Order Quantity Decisions

TranZact doesn’t run an automatic EOQ calculation, but it gives you the real demand and cost data the formula needs: stock valuation and consumption history tracks actual usage per SKU, warehouse-wise real-time tracking shows current stock before a new order gets placed, and the MRP engine plans purchases from confirmed demand rather than a static reorder quantity.

It doesn’t replace the judgment call on vendor discounts or seasonal buffers. What it removes is calculating EOQ off stale or guessed demand numbers in the first place.

FAQs

What is Economic Order Quantity (EOQ)?

EOQ is the order quantity that minimizes the combined cost of ordering and holding inventory, calculated from annual demand, cost per order, and holding cost per unit.

What is the EOQ formula?

EOQ equals the square root of (2 times annual demand times ordering cost) divided by holding cost per unit per year. It’s the quantity where ordering cost per unit and holding cost curves cross.

Why doesn’t the EOQ formula work well for many manufacturing SMEs?

Because it assumes constant demand, a fixed reliable lead time, and a known flat holding cost, conditions that rarely hold for seasonal products, new SKUs, or vendors with inconsistent delivery.

What is the difference between EOQ and reorder point?

EOQ answers how much to order each time. Reorder point answers when to place that order, the stock level that triggers a new purchase. The two work together, not as substitutes.

Does EOQ account for bulk purchase discounts?

Not in its basic form. The classic formula assumes a flat unit price regardless of order size, so quantity discounts need a separate adjustment, sometimes called the EOQ with price breaks model.