Inventory Carrying Cost

How to calculate inventory carrying cost

Carrying cost is what it costs to own stock for a year, expressed as a share of what the stock is worth. A 22% rate means that every $100 of inventory costs $22 a year to hold. It is a real cost even when no invoice arrives for most of it, because much of it is the return you give up by tying money up in inventory.

Add up four groups of costs, then divide by the average value of the inventory you carried. The result feeds reorder decisions, pricing on slow movers and clearance timing.

The four components

Capital cost is usually the largest and the most often forgotten, because owner-funded inventory has no interest bill. It still has an opportunity cost: the same money in a loan payoff or another investment would earn a return. Use your borrowing rate, or what you would earn elsewhere.

Risk cost is the most variable. Fashion, electronics and perishables lose value quickly, while durable goods hold it. The same guide cites total carrying costs of about 20% to 30% for general e-commerce and higher for food and perishables (30% to 40%), with automotive parts nearer 15% to 22%. Ranges like these are a sanity check for your own calculation, not a substitute for it.

Worked example

An online retailer carries $250,000 of inventory on average. The annual costs of holding it are below.

The carrying cost rate is $55,500 ÷ $250,000 = 22.2%. Carrying inventory costs the business $55,500 a year, before a single sale.

What it does to the margin on a single item

Apply the rate to one product. A unit costs the retailer $40 and sells for $70, a $30 gross margin. At 22.2%, holding that unit costs $40 × 22.2% = $8.88 a year, or $0.74 a month.

A slow mover that sits for a year gives up almost 30% of its margin ($8.88 of $30) before any discounting. That is why a product with a strong gross margin on paper can still be a weak performer once holding time is included. The inventory turnover and days inventory outstanding figures tell you how long stock is really sitting.

One rate does not fit every product

The 22.2% rate is a blend. Risk cost differs sharply between products, so the true rate does too. Keep capital (10%), warehouse (3.6%) and service (2.2%) costs the same and change only the risk cost:

Ten points of extra risk add $10,000 of annual cost on the same amount of stock. Use a category rate, or at least a separate rate for the fast-obsolescing lines, when you judge which products deserve shelf space.

The rate also helps with clearance timing. Take 1,000 units of seasonal apparel that cost $40 and list at $70. At 27.8%, holding a unit for six more months costs $40 × 27.8% × 0.5 = $5.56, and holding it a full year costs $11.12. A 10% markdown costs $7.00 a unit. If you expect to sell at full price within six months, holding is cheaper than marking down. If it will take a year, marking down now costs less than waiting, and that is before you count the chance that the item never sells at all.

Carrying cost and how much to order

Holding cost pulls against ordering cost. Large orders mean fewer purchase orders, but more stock sitting on the shelf. The economic order quantity balances the two: EOQ = √(2 × annual demand × cost per order ÷ holding cost per unit).

With 12,000 units of annual demand, $50 per order and the $8.88 holding cost per unit from above, EOQ = √(2 × 12,000 × 50 ÷ 8.88) = √135,135 ≈ 368 units. Order in batches near that size. If you ignored capital and risk and counted only warehouse and insurance ($2.32 per unit), EOQ would come out near 719 units, so you would order almost twice as much as the true economics justify. See economic order quantity and safety stock for how cushion stock fits in.

How to reduce carrying costs

• Increase turns. Faster-moving stock reduces every component at once. Track the slowest 20% of SKUs first.
• Clear dead stock early. A markdown taken in month three usually costs less than the carrying cost, obsolescence risk and eventual write-off of holding it for a year.
• Order closer to demand. Use a demand forecast and reorder points instead of round-number bulk orders.
• Negotiate supplier terms. Longer payment terms or consignment reduce the capital tied up.
• Trim the range. Each extra SKU adds safety stock and handling. Products that sell rarely often cost more to keep than they earn.

Cutting stock too far has its own cost: stockouts lose sales. Set a target service level, then reduce inventory to the amount that meets it. The inventory carrying cost calculator shows the trade-off, and working capital explains why inventory decisions also affect cash.

Common mistakes

• Leaving out the cost of capital. In the example, capital is 10 of the 22.2 points. Without it the rate falls to 12.2%, about 45% too low.
• Dividing by cost of goods sold instead of average inventory. The rate is a share of the value held, so use the balance you carry.
• Using one rate for every item. Perishable, fast-obsolescing and bulky items cost more to hold than durable, compact ones.
• Ignoring shrinkage. Theft, damage and count errors are part of risk cost. See inventory shrinkage.
• Treating a year-end balance as the average. Seasonal businesses carry far more stock than their year-end figure suggests.

What carrying cost can't tell you

The rate is an estimate built from allocations, and it doesn't include the lost sales when you run out. It also can't tell you which products deserve the space. For that, compare each product's margin after carrying cost, and use the rate as one input into reorder and clearance decisions rather than as a precise number.

Frequently asked questions