Use a consistent period and cost definition. This measure helps explain a decision, but it is not the same as gross margin, cash in the bank or net profit.
Build the cost list from the sale
For a fictional stationery order, start with the amount the business earns from the customer. Decide how taxes collected on behalf of others, refunds and discounts are treated in the relevant records. Then identify costs that change with the orders being analyzed.
| Fictional order | Amount |
|---|---|
| Selling price | $80 |
| Product cost | $35 |
| Packaging | $3 |
| Order-specific fulfillment | $5 |
| Payment cost | $2 |
| Total variable cost | $45 |
| Unit contribution | $35 |
The figures are teaching assumptions, not typical stationery economics. A fee can have both a variable element and a recurring minimum. Separate those parts when the decision calls for it.
Avoid allocating every cost into one order
Suppose the company also pays $2,000 of fixed monthly operating costs. At 100 orders, revenue is $8,000, variable cost $4,500 and total contribution $3,500. Subtracting that fixed cost produces a simplified $1,500 operating result before other excluded items.
At 50 orders, total contribution is $1,750 and the simplified result is −$250. Unit contribution is still $35 in this scenario. The change is how much total contribution exists to cover the fixed cost.
Allocating the fixed $2,000 evenly across current orders can help some reporting purposes. But treating that allocation as a cost that necessarily rises with each additional order can mislead a short-term incremental decision. Conversely, assuming fixed costs never change is also wrong when extra activity requires another shift or facility.
Use the relevant range
Cost behavior depends on the workload and time horizon. Salaried staff may be fixed over a small volume change but increase when another person is needed. Shipping charges may change by package size, destination or negotiated tier. The $45 variable cost should therefore be tested against the scenario you are considering.
If acquisition spending is incurred for only some new customers, show it separately rather than charging every organic repeat order the same assumed acquisition cost. If repeat purchases are included, explain their evidence and timing.
Translate the measure into a decision
For a price change, compare total contribution at the expected new volume. For a capacity choice, investigate whether more good completed sales are possible. For cash planning, place the actual receipts and payments on a calendar.
These questions are related but not interchangeable. Start with margin vs markup if percentage labels are unclear. Use the price calculator for a bounded scenario and profit vs cash flow for payment timing.
Your worksheet
Choose one product, service or customer segment. List price, each variable cost and the basis for that classification. Calculate unit and total contribution for the current period. Add the fixed costs needed for that volume and note costs omitted from the illustration.
Then change one assumption. If volume doubles, does unit cost stay constant? If price falls, how many extra sales are required? The discount-volume guide explains that second calculation.
Sources and limits
The definitions follow OpenStax's managerial-accounting explanation. The stationery example and scenarios are original HBW calculations. Taxes, financing, inventory timing and costs not listed are excluded from the simplified operating result.