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Inventory & supply chain

Inventory carrying cost calculator — rate and annual cost

Build your inventory carrying cost rate from capital, storage, service and risk. Get the annual cost, the percentage rate, and holding cost per unit.

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Short answer

Inventory carrying cost is the annual cost of holding stock, stated as a percentage of average inventory value. Add capital, storage, service and risk costs, then divide by average inventory. On $1,050,000 of average inventory, $225,950 of annual carrying cost is a 21.5% rate. Most operations land in the high teens to high twenties.

Inventory carrying cost is what it costs to own stock for a year rather than to buy it. It is the number that makes order quantities, buffer levels and slow-mover decisions arguable with a CFO instead of a matter of opinion.

Enter your average inventory value and the four components. The calculator returns the carrying rate as a percentage, the annual cost in dollars, the monthly equivalent, the holding cost per unit that the EOQ formula needs, and what a reduction in stock would be worth.

Almost everyone underestimates this rate, because capital and space are visible while obsolescence arrives quietly as a write-off at year-end.

Your numbers

$

At cost, averaged across the year. A year-end low understates every percentage below.

Capital
% per year

Your WACC or marginal borrowing rate — the return this money would earn elsewhere.

Storage
How do you know storage cost?
$

Space, utilities, racking, handling equipment, putaway and movement labour. Owned space is not free — use the rent forgone.

Service
% per year
% per year
$

Count hours at a loaded rate, plus WMS and scanning costs. A headcount figure, so enter it in dollars.

Risk
% per year

Three years of actual write-offs ÷ average inventory. Use history, not the reserve policy.

% per year

Net inventory adjustments from counts.

Apply it
$

Converts the rate into holding cost per unit per year — the H in the EOQ formula.

%

Shows the one-off cash release and the recurring carrying cost avoided.

Result

Annual carrying cost rate
21.5%

$225,950 a year on $1,050,000 of average inventory, or 1.79% a month

Annual carrying cost$225,950
Monthly carrying cost$18,829
Cost to hold $10,000 for a year$2,152
Holding cost per unit per year (H)$3.98
Cash released by a 10% reduction$105,000
Carrying cost avoided each year$22,595
Capital9.5% · $99,750
Storage5.9% · $62,000
Service2.9% · $30,600
Risk3.2% · $33,600
Capital = $1,050,000 × 9.50% = $99,750
Storage = $62,000 entered directly
Service = $1,050,000 × 1.20% + $18,000 = $30,600
Risk = $1,050,000 × 3.20% = $33,600
Total = $225,950 ÷ $1,050,000 = 21.5%
21.5% sits in the band most operations land in. Holding cost per unit is $3.98 a year at a $18.50 unit cost — use that as the H in your order-quantity maths rather than a separate estimate.

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The formula

Carrying rate % = (Capital + Storage + Service + Risk) ÷ Average inventory value × 100
Capital
Average inventory value × your cost of capital. The return the money would earn somewhere else in the business.
Storage
Space and handling: rent or opportunity cost of the space, utilities, racking, forklifts, warehouse labour attributable to holding.
Service
Insurance, inventory and property taxes on stock, cycle counting labour, and the systems cost of tracking it.
Risk
Obsolescence and write-offs, shrinkage, damage and spoilage. Usually the largest component people forget.
Average inventory value
Average balance at cost over the year, not the closing balance. A year-end low understates the rate.

Holding cost per unit per year — the H in the EOQ formula — is this rate multiplied by unit cost, not a separately estimated number.

Worked example

Average inventory value
$1,050,000
Cost of capital
9.5%
Annual storage cost
$62,000
Insurance and inventory taxes
0.65% + 0.55%
Cycle counting and systems
$18,000
Obsolescence and shrink
2.4% + 0.8%
Result
21.5% carrying rate · $225,950 a year · $3.98 per unit at an $18.50 unit cost

Capital is $1,050,000 × 9.5% = $99,750. Storage is $62,000. Service is $1,050,000 × 1.2% = $12,600 plus $18,000 of counting and systems, so $30,600. Risk is $1,050,000 × 3.2% = $33,600. Total $225,950 ÷ $1,050,000 = 21.5%, or about 1.79% a month. Every $10,000 of stock held for a year costs $2,152.

What belongs in each component

The four buckets exist to stop double counting and to make the estimate arguable line by line. Warehouse labour is the usual boundary dispute: picking and shipping belong to fulfilment, while putaway, moving and counting belong to holding.

ComponentWhat goes inWhere the number comes from
CapitalThe return forgone on money tied up in stock.Your WACC, or the marginal borrowing rate if you are drawing on a facility. Not the risk-free rate.
StorageRent or space opportunity cost, utilities, racking, handling equipment, putaway and movement labour.Warehouse cost centre, allocated by the share of space inventory actually occupies.
ServiceInsurance, inventory and property taxes, cycle counting, WMS and barcode systems.Insurance schedule, tax assessments, count hours × loaded rate.
RiskObsolescence, write-downs, shrink, damage, spoilage, currency exposure on imports.Three years of write-off history divided by average inventory. Use actuals, not the policy.

Where the rate gets understated

  • Obsolescence booked as an operating expense. Write-offs land in a cost centre far away from inventory and never make it back into the holding rate.
  • Owned warehouse space treated as free. If you own the building, the cost is the rent you could charge or the sale value forgone. Zero is the wrong entry.
  • Cost of capital set at the deposit rate. Money in stock competes with everything else the business could fund. Use the rate the CFO uses for capital projects.
  • Closing inventory instead of the average. Businesses that draw stock down for year-end report a rate several points too low all year.
  • Only counting rate-based components. Insurance is a rate; counting labour is a headcount. Mixing dollar amounts and percentages is correct, and forcing everything into a percentage loses the fixed piece.

What the rate is actually for

A carrying rate is an input, not a KPI. Three decisions depend on it. Order quantity: holding cost per unit per year is the H in EOQ, so a rate that is four points too low pushes every order quantity too high — check yours in the EOQ calculator.

Buffer sizing: safety stock costs the carrying rate every year and buys service level, which is a trade you can only price once the rate is known. And slow movers: at 21.5%, holding $56,100 of C-class stock costs about $12,072 a year, which is the number that decides whether to discount it or keep it. Rank the tail first with the ABC analysis calculator.

Assembling the components from the ERP

Two of the four components are already in your general ledger — insurance and warehouse cost centres — and two need history: write-offs and shrink adjustments over several years, matched against average inventory for the same periods. That is a GL query plus an inventory adjustment query, on the same period basis.

With you ask for the pieces: "inventory write-offs and shrink adjustments by year against average inventory value". It computes from your own account and shows the query, so the write-off account list is visible rather than assumed.

Frequently asked questions

How do you calculate inventory carrying cost?

Add the four cost groups for a year — capital, storage, service and risk — then divide the total by average inventory value. For example, $225,950 of annual holding cost against $1,050,000 of average inventory is a 21.5% carrying rate. Multiply the rate by unit cost to get holding cost per unit per year.

What is a typical inventory carrying cost percentage?

Most operations land somewhere in the high teens to high twenties once obsolescence and the real cost of space are included. Treat any single figure as directional: a refrigerated food distributor and a fastener wholesaler have genuinely different rates. Build your own from your cost of capital and your own write-off history instead of adopting a benchmark.

Does inventory carrying cost include the cost of the goods?

No. Carrying cost is the cost of holding stock for a period, not the purchase cost of the stock itself. The purchase price belongs in COGS and in landed cost. Carrying cost is expressed as a percentage of inventory value precisely so it can sit alongside the purchase cost without double counting it.

Why is my carrying cost rate below 15%?

Usually because a component is missing. The two most common gaps are obsolescence, which is often booked as an operating expense far from inventory, and owned warehouse space treated as free. A cost of capital set at a deposit rate rather than the company's WACC is the third. Check those three before accepting a low rate.

How does carrying cost affect order quantity?

Holding cost per unit per year is the denominator in the EOQ formula, so a rate that is too low produces order quantities that are too large. At a 21.5% rate and an $18.50 unit cost, holding cost is $3.98 per unit per year. Understating that at 12% would give $2.22 and inflate the order quantity by roughly a third.

How much do I save by cutting inventory by 10%?

Two separate benefits. The cash release is one-off and equals 10% of average inventory value, so $105,000 on a $1,050,000 average. The recurring saving is that amount times the carrying rate, about $22,595 a year at 21.5%. Only the variable components come off immediately, so treat the recurring figure as an upper bound.

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