• Incremental cost (also called marginal cost) is the extra cost a firm incurs to produce one additional unit of output or to increase production by a defined amount.
– Incremental costs are composed of variable costs (raw materials, direct labor, incremental utilities, etc.). Fixed costs are typically excluded unless they change with the decision.
– Comparing incremental cost to incremental revenue (marginal revenue) is central to short‑term decisions such as special orders, make‑or‑buy choices, product‑line changes and pricing.
– Use incremental‑cost analysis to improve efficiency, evaluate opportunities, and determine whether increased production or a specific order will be profitable.
What incremental cost means
Incremental cost is the change in total cost that results from producing an additional unit or an increment of units. Mathematically:
Incremental cost = Change in total cost / Change in quantity produced
Because only costs that change with production volume are relevant, incremental cost analysis typically focuses on variable costs. Fixed costs (rent, core factory overhead, most equipment depreciation) are excluded unless they will change as a direct result of the decision.
Key concepts
– Marginal cost vs incremental cost: Often used interchangeably. Marginal cost usually refers to the cost of one additional unit; incremental cost can also be applied to blocks of units.
– Variable costs: Costs that rise and fall with production — raw materials, direct labor, per‑unit energy, shipping tied to volume.
– Step or semi‑variable costs: Some costs jump at threshold levels (e.g., adding a second production line). Treat them carefully: for small increments they may be fixed, but for larger increments they become incremental.
– Economies of scale: As output increases, average cost per unit often falls because fixed costs are spread over more units; incremental cost per unit can be below average cost.
What incremental costs include (typical)
– Direct materials and components required for each additional unit
– Direct labor hours incurred only if output rises
– Incremental utilities, consumables, and maintenance associated with added production
– Piece‑rate or overtime wages paid only for incremental output
– Incremental shipping, packaging and handling tied to extra units
– Any additional supplier fees or temporary costs (e.g., setup for a special run)
What incremental costs usually exclude
– Existing fixed rent, standard factory depreciation and salaried overhead that will not change with the incremental decision
– Sunk costs (past expenditures) — they are irrelevant to current decisions
Practical example (simple)
Current production: 10,000 units; total cost = $300,000
Proposed production: 12,000 units; total cost = $330,000
Change in quantity = 2,000 units
Change in total cost = $330,000 − $300,000 = $30,000
Incremental cost per extra unit = $30,000 / 2,000 = $15 per unit
Decision application: If a special order offers $20 per unit for 2,000 units, it covers the $15 incremental cost and contributes $5 per unit to fixed costs and profit, so acceptance may be beneficial (subject to capacity and strategic considerations).
Comparing incremental cost and incremental revenue
Decision rule (short run):
– If incremental revenue (price × incremental units) > incremental cost → the increment increases profit.
– If incremental revenue incremental cost and there is spare capacity, accept; otherwise reject.
– Make‑or‑buy: Include incremental costs of producing internally (materials, labor, incremental overhead) and compare to the buy price; add opportunity cost if internal capacity can produce higher‑margin items.
– Discontinue product: Consider the avoided incremental costs and lost incremental revenue; if discontinuing eliminates only unallocated fixed costs then it may not improve profitability.
Relevant KPIs and metrics
– Incremental cost per unit
– Contribution margin per incremental unit = Price − Incremental cost per unit
– Incremental profit = Incremental revenue − Incremental cost
– Break‑even incremental volume for a specific price or cost change
How incremental‑cost analysis helps companies
– Improves short‑term decision making by focusing on costs that change with the decision.
– Identifies whether promotions or special orders add or destroy value.
– Helps determine the most profitable product mix when capacity is constrained.
– Supports decisions about outsourcing, capacity additions, and pricing strategies.
– Drives continuous improvement by highlighting variable cost drivers where process improvements can lower incremental costs.
The bottom line
Incremental cost analysis isolates the extra costs tied directly to a change in production or an offer. It is a practical tool for short‑run decisions — special orders, make‑or‑buy, product changes and tactical pricing — because it concentrates only on the costs that will actually change. Properly applied, incremental cost analysis helps firms accept profitable opportunities, avoid loss‑making ones, and use capacity more efficiently. Always watch for step costs, capacity limits, and longer‑term fixed‑cost implications before making strategic decisions.
Source
– Jake Shi, “Incremental Cost,” Investopedia. Accessed at (source provided by user).