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Wilson EOQ, with the math
Concept

Inventory holding cost (H)

Direct answer

Holding cost H is the annual cost of carrying one unit in inventory. It decomposes into five components: cost of capital (5 to 10 percent), storage and warehouse (2 to 5 percent), services (insurance, IT, 1 to 2 percent), risk (shrinkage, damage, 1 to 3 percent), and obsolescence (variable, 2 to 20 percent depending on category). Defensible SMB total: 20 to 30 percent of unit cost for stable goods[1].

Concept
H (annual holding cost per unit)

Cost of holding one unit in inventory for one year, in $ per unit per year.

H = i * C
When it matters: H is the denominator of Q* = sqrt(2DS/H). Doubling H shrinks Q* by sqrt(2), about 29 percent. The cost curve is flat near Q*, so mis-estimating H by 3 to 5 points moves Q* by 6 to 10 percent, not catastrophically.

The five components

How to express H

Two equivalent forms. Per-unit-per-year: H = $12/unit/year. Percent-of-unit-cost:i = 30 percent, with H derived as i * C inside the Wilson formula. The percent form is usually easier to defend to a CFO because each component is a natural percent (capital cost, warehouse cost as percent of inventory value, and so on)[2].

How to defend H without overstating

Show the decomposition explicitly. "Our 25 percent carrying cost is 8 capital + 4 warehouse + 2 service + 2 risk + 9 obsolescence" is defensible. "Industry standard" is not. The carrying-cost percentage page walks the component-by-component build-up.