Inventory Cost

What Inventory Really Costs: Carrying Cost, Landed Cost, and Stockout Cost

Where inventory dollars actually go: carrying cost components, landed cost drivers, stockout exposure, and the price variance that erodes a quoted saving.

The price on a purchase order is rarely the real cost of holding a part. True cost per unit stacks four buckets: landed acquisition cost, annual carrying cost, stockout exposure, and price variance against your standard. A part quoted at 4.20 dollars can cost you 6.50 or more once freight, duty, capital, and the risk of running dry are counted. Estimators who quote off unit price alone lose margin quietly. This breakdown shows where the money goes and how to build a defensible number using the Inventory Carrying Cost, Landed Cost, and Stockout Cost calculators, without re-deriving the formulas.

Carrying cost is the biggest hidden line and typically runs 18 to 30 percent of inventory value per year. It splits into cost of capital at 8 to 15 percent depending on your hurdle rate, storage and handling at 2 to 5 percent, insurance and taxes near 1 to 3 percent, and obsolescence, shrinkage, and damage at 2 to 8 percent for volatile categories. On 1.2 million dollars of average inventory at a 25 percent carrying rate, you burn 300000 dollars a year just to hold stock. Cut average inventory by 200000 dollars and you save 50000 annually, which is the real prize behind a turnover improvement.

Landed cost is where a cheap quote turns expensive. Freight, duty, insurance, and broker fees commonly add 15 to 30 percent over the ex-works price on imported goods. A 6.5 percent duty, ocean freight near 8 percent of value, and 3 to 5 percent in insurance and handling stack fast. Tariff swings hit hardest: a jump from 6.5 to 25 percent on a 4.20 dollar base adds 0.78 per unit, wiping out a two-year sourcing saving overnight. Run every offshore quote through the Landed Cost Calculator and the Tariff Impact Calculator before you compare it to a domestic supplier.

Stockout cost is the line most quotes ignore, and it is often larger than carrying cost. It combines lost margin on missed sales, expedite freight, and customer penalties. If a stockout forces air freight at 3.50 per unit versus 0.35 by ocean, that single expedite costs 3.15 extra per unit, ten times the normal freight. Add lost contribution margin: on a 12 dollar item at 35 percent margin, each unit not shipped forfeits 4.20. The Stockout Cost Calculator monetizes this so you can justify the safety stock that carrying-cost math alone would tell you to cut.

Purchase price variance is the gap between the price you actually paid and the standard cost in your system, and it silently rewrites your quote. If standard cost is 4.20 and you paid 4.55 after a mid-year surcharge, PPV is 0.35 unfavorable per unit, or 175000 dollars on 500000 units a year. Favorable PPV can be just as misleading if it comes from a bulk buy that inflates carrying cost. Track it per commodity in the Purchase Price Variance calculator so a supplier's headline discount is checked against what you truly paid at the dock.

Building a defensible cost per unit means adding the buckets, not picking one. Start with landed cost at 5.04, add carrying cost as landed times the carrying rate times average days held over 365. Hold that unit 46 days at a 25 percent rate: 5.04 times 0.25 times 46 over 365 equals 0.159 per unit in carrying charges. Add an amortized stockout reserve, say 0.05 per unit based on historical shortage frequency, and your fully loaded cost is about 5.25. Quote off 4.20 and you are 25 percent light before overhead.

Estimates go wrong in predictable places. Using list freight instead of contracted rates overstates cost by 10 to 20 percent on high-volume lanes. Ignoring minimum order quantities buries you in carrying cost when a 10000 unit MOQ against 400 per day demand means 25 days of forced stock. Forgetting duty on the freight-inclusive value, not just goods value, understates landed cost by a few points. And applying a single carrying rate across all SKUs overcharges stable commodities and undercharges electronics that obsolesce at 15 to 20 percent a year.

Score suppliers on total cost, not unit price, before you award. A supplier 0.10 cheaper per unit but three days slower on lead time forces extra safety stock whose carrying cost can exceed the saving. Combine the Supplier Scorecard with landed and carrying numbers so the award reflects delivered, held, and risk-adjusted cost. On a 500000 unit program, a 0.10 saving is 50000 a year, but if the slower supplier adds 900 units of safety stock at 5.04 landed and a 25 percent carrying rate, that is 1134 dollars a year that only partly offsets and comes with higher stockout risk.

Published 2026-07-01.