EOQ calculator: economic order quantity for spare parts
How many of a part to order at a time so the cost of ordering and the cost of keeping stock on the shelf are lowest together, with orders per year and the total yearly cost.
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Economic order quantity 173 units Orders per year 6.9about every 53 days Yearly ordering cost $346 Yearly holding cost $346average stock is half an order Stop working this out by handFleetZap keeps parts stock with reorder points and low-stock alerts, and turns them into purchase orders to your vendors.
See FleetZap Maintenance · Try the demoThe formula
EOQ = √(2 × Yearly demand × Cost per order ÷ Holding cost per unit per year)
At the EOQ, ordering cost and holding cost are equal, which is where their total is lowest. With the defaults: √(2 × 1,200 × $50 ÷ $4) ≈ 173 units an order, about 7 orders a year.
Using the numberWhat to do with it
- EOQ assumes steady use. Use it for parts you go through every week (filters, oil, wear parts), not for critical spares you might need once.
- Round to the pack size your vendor sells, then check the order still lands near the EOQ.
- Pair it with a reorder point so you know when to place each order, not only how much.
Guides behind this calculator
Spare parts inventory ABC inventory analysis Parts inventory softwareMore free calculators
Downtime cost calculator MTBF calculator OEE calculator Equipment cost per hour calculator Equipment depreciation calculator Equipment rental rate calculator Next PM due calculator Safety stock calculator Reorder point calculatorFleetZap Maintenance
The heart of FleetZap, and everything a maintenance team needs in one place: work orders and preventive maintenance, inspections and the field app, plus a parts store with purchasing, compliance and certificate tracking, multi-location assets with a full lifecycle, and the KPIs that prove it’s working.
- Work orders
- Preventive maintenance
- Procedures, inspections & field app
- Parts & purchasing
- Compliance
- Assets, reports & KPIs
Good to know
What is the EOQ formula?EOQ is the square root of (2 × yearly demand × cost per order ÷ holding cost per unit per year). With 1,200 units a year, $50 an order and $4 a year to hold each unit, EOQ is about 173 units.
When should you not use EOQ for spare parts?EOQ assumes steady, predictable use. It fits filters, oil and wear parts, but not critical spares used once in a while, where the question is whether to keep one on the shelf at all.
What goes into holding cost?Storage space, the money tied up in stock, insurance, and parts that get lost, damaged or go obsolete. Many businesses use a share of the part's price per year as an estimate.
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