How do you calculate inventory obsolescence cost?

Multiply the at-risk units by their carrying value per unit, weight by the probability the stock goes obsolete, then add fixed disposal and write-off costs. With 100 at-risk units at $45 each, an 80% obsolescence probability, and $250 in disposal cost, the expected loss is $3,850.

What is a good inventory obsolescence rate?

World-class operations keep excess-and-obsolete inventory under 1-3% of total inventory value; above 5% signals weak demand planning or slow disposition. The right target depends on how fast your product portfolio churns.

What is the difference between obsolete and excess inventory?

Excess is more of a sellable item than demand will consume in a reasonable horizon; obsolete stock has no remaining demand at all, superseded, expired, or discontinued. Excess can often be run down over time; obsolete usually heads to write-off or scrap.

How is obsolescence cost different from carrying cost?

Carrying cost is the ongoing expense of holding inventory, storage, insurance, capital. Obsolescence cost is the one-time expected loss when that inventory can no longer be sold or used. A part accrues carrying cost every month and then hits you with obsolescence cost when demand dies.

Why weight by a probability instead of writing off the full value?

Not all at-risk stock actually goes dead, some finds a last-time-buy customer or a service-parts home. In the example, an 80% probability on $4,500 of material yields $3,600 of expected variable loss, a more honest reserve than either zero or the full value.

Should the disposal cost be included in the reserve?

Yes. Scrapping, recycling fees, and the labor to write material off the books are real cash costs. The $250 fixed cost in the example is added on top of the probability-weighted material loss so the reserve reflects total exposure, not just lost material value.

Supply Chain & Procurement calculator

Inventory Obsolescence Cost Calculator

Inventory obsolescence cost is the expected dollar loss from stock that will never sell or be consumed, parts superseded by an engineering change, excess safety stock, or components tied to a phased-out product. Controllers, materials planners, and operations leaders calculate it to size the obsolescence reserve, justify write-offs, and decide whether to discount, return, or scrap aging inventory before it fully sours. It is a silent margin killer: material that looked like an asset on the balance sheet becomes a liability the moment demand disappears, and the longer it sits the more it costs to carry, store, and eventually dispose of. Putting a probability-weighted number on it turns a vague worry into a line item you can act on.

What this calculator does

Estimate obsolete inventory cost from at-risk value and write-down rate.
Use it when inventory obsolescence cost in supply chain and procurement is being put through a supply chain and procurement weighted-cost review.
It computes the expected obsolescence loss by weighting the carrying value of at-risk units by the probability they go dead, then adding fixed disposal and write-off costs.

Formula used

Weighted cost = quantity × rate × capture factor + fixed adjustment

Inputs explained

At-risk units in inventory:
Carrying value per unit:
Probability of obsolescence:
Fixed disposal and write-off cost:

How to use the result

Use it during quarterly reserve reviews, after an engineering change or product end-of-life, or when an excess-and-obsolete report flags a lot of slow-moving stock.
The probability of obsolescence is an estimate, if demand recovers or the part gets a last-time-buy home, actual loss is lower; if the material is hazardous or hard to dispose, the fixed cost can run well above the figure entered.

Current U.S. benchmarks

U.S. manufacturing runs at 76.0% of capacity (Federal Reserve, Jul 2026). New factory orders are up 7.4% year over year (Census).
Importers paid an average effective tariff of 12.4% of customs value in 2025 across the 57 manufacturing import families MFG Calcs tracks (USITC DataWeb), up from 3.3% the year before. Statutory and effective rates by family, with top source countries, are at mfgcalcs.com/tariffs.
Sourcing currencies as of 2026-08-21 (Federal Reserve H.10): 6.721 CNY and 16.8909 MXN per USD. Landed-cost comparisons move with these daily rates.

Common questions

How do you calculate inventory obsolescence cost? Multiply the at-risk units by their carrying value per unit, weight by the probability the stock goes obsolete, then add fixed disposal and write-off costs. With 100 at-risk units at $45 each, an 80% obsolescence probability, and $250 in disposal cost, the expected loss is $3,850.
What is a good inventory obsolescence rate? World-class operations keep excess-and-obsolete inventory under 1-3% of total inventory value; above 5% signals weak demand planning or slow disposition. The right target depends on how fast your product portfolio churns.
What is the difference between obsolete and excess inventory? Excess is more of a sellable item than demand will consume in a reasonable horizon; obsolete stock has no remaining demand at all, superseded, expired, or discontinued. Excess can often be run down over time; obsolete usually heads to write-off or scrap.
How is obsolescence cost different from carrying cost? Carrying cost is the ongoing expense of holding inventory, storage, insurance, capital. Obsolescence cost is the one-time expected loss when that inventory can no longer be sold or used. A part accrues carrying cost every month and then hits you with obsolescence cost when demand dies.
Why weight by a probability instead of writing off the full value? Not all at-risk stock actually goes dead, some finds a last-time-buy customer or a service-parts home. In the example, an 80% probability on $4,500 of material yields $3,600 of expected variable loss, a more honest reserve than either zero or the full value.

Last reviewed 2026-07-13.