How do you calculate spare parts carrying cost?

Multiply average inventory value by the annual carrying cost rate and the share of inventory included, then add fixed storeroom overhead. With $850,000 in inventory at an 0.18 rate across 100% of stock plus $32,000 fixed cost, the total is $185,000 per year.

What is a good carrying cost rate for spare parts?

Most MRO storerooms land between 18% and 25% per year once you include capital, space, insurance, shrinkage, and obsolescence. The 0.18 default is a conservative blended figure; critical slow-movers with high obsolescence risk often justify a higher rate.

Why is the variable cost $153,000 in the example?

The variable portion is inventory value times rate times coverage: $850,000 x 0.18 x 100% = $153,000. Adding the $32,000 fixed storeroom and CMMS cost gives the $185,000 total.

Does carrying cost include the purchase price of the part?

No. Carrying cost is the recurring annual cost of holding the part — capital opportunity cost, storage, insurance, obsolescence. The purchase price is a separate one-time acquisition cost.

How can I reduce spare parts carrying cost?

Cut the inventory value through min/max optimization, vendor-managed inventory, or sharing critical spares across sites, and reduce obsolescence by reviewing dead stock annually. Lowering the $850,000 base directly shrinks the $153,000 variable cost.

Carrying cost vs stockout cost — which matters more?

They trade off. Carrying cost is certain and recurring; stockout cost is probabilistic but can dwarf it for critical assets. Optimize both together rather than minimizing carrying cost alone.

CMMS, EAM & Spare Parts Management calculator

Spare Parts Carrying Cost Calculator

Spare parts carrying cost is the total annual expense of holding MRO inventory in your storeroom — not just the capital tied up, but the insurance, obsolescence, shrinkage, space, and the CMMS and staff that keep it organized. Maintenance and reliability managers use it to justify min/max changes, criticality-based stocking, and storeroom consolidation. It matters because spare parts inventory is one of the largest hidden costs in any asset-intensive plant: a storeroom can easily cost 18-25% of its book value every year just to sit there. Knowing the number turns a vague 'we have too many spares' feeling into a defensible budget line.

What this calculator does

Estimate annual carrying cost for spare parts inventory using stocked value, carrying-rate assumptions, and fixed storeroom cost.
a maintenance or asset-management team needs to quantify inventory carrying cost, compare stocking strategies, or challenge excess and obsolete MRO inventory for a MRO storeroom
It computes the total annual carrying cost of spare parts as the inventory value multiplied by the carrying rate and analysis coverage, plus fixed storeroom and system overhead.

Formula used

Variable spare parts carrying cost = average spare parts inventory value × annual carrying cost rate × inventory value included in analysis
Total spare parts carrying cost = variable spare parts carrying cost + fixed storeroom handling and system cost

Inputs explained

Average spare parts inventory value:
Annual carrying cost rate:
Inventory value included in analysis:
Fixed storeroom handling and system cost:

How to use the result

Use it during annual storeroom budgeting, inventory optimization projects, or when building the business case for write-offs of obsolete spares.
The carrying rate is an industry estimate, not a precise per-part figure — obsolescence risk on slow-moving critical spares can push the true rate well above the blended number you enter.

Common questions

How do you calculate spare parts carrying cost? Multiply average inventory value by the annual carrying cost rate and the share of inventory included, then add fixed storeroom overhead. With $850,000 in inventory at an 0.18 rate across 100% of stock plus $32,000 fixed cost, the total is $185,000 per year.
What is a good carrying cost rate for spare parts? Most MRO storerooms land between 18% and 25% per year once you include capital, space, insurance, shrinkage, and obsolescence. The 0.18 default is a conservative blended figure; critical slow-movers with high obsolescence risk often justify a higher rate.
Why is the variable cost $153,000 in the example? The variable portion is inventory value times rate times coverage: $850,000 x 0.18 x 100% = $153,000. Adding the $32,000 fixed storeroom and CMMS cost gives the $185,000 total.
Does carrying cost include the purchase price of the part? No. Carrying cost is the recurring annual cost of holding the part — capital opportunity cost, storage, insurance, obsolescence. The purchase price is a separate one-time acquisition cost.
How can I reduce spare parts carrying cost? Cut the inventory value through min/max optimization, vendor-managed inventory, or sharing critical spares across sites, and reduce obsolescence by reviewing dead stock annually. Lowering the $850,000 base directly shrinks the $153,000 variable cost.

Last reviewed 2026-05-12.