# Contribution margin

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Contribution margin, or dollar contribution per unit, is the selling price per unit minus the variable cost per unit. “Contribution” represents the portion of sales revenue that is not consumed by variable costs and so contributes to the coverage of fixed costs. This concept is one of the key building blocks of break-even analysis.[1]

Decomposing Sales as Contribution plus Variable Costs. In the Cost-Volume-Profit Analysis model, costs are linear in volume.

In cost-volume-profit analysis, a form of management accounting, contribution margin—the marginal profit per unit sale—is a useful quantity in carrying out various calculations, and can be used as a measure of operating leverage. Typically, low contribution margins are prevalent in the labor-intensive tertiary sector while high contribution margins are prevalent in the capital-intensive industrial sector.

## Construction

The Unit Contribution Margin (C) is Unit Revenue (Price, P) minus Unit Variable Cost (V):

$\text{c} = \text{p} - \text{v}$[1]

The Contribution Margin Ratio is the percentage of Contribution over Total Revenue, which can be calculated from the unit contribution over unit price or total contribution over Total Revenue:

$\frac{\text{C}}{\text{P}}=\frac{\text{P}-\text{V}}{\text{P}}=\frac{\text{Unit Contribution Margin}}{\text{Price}}=\frac{\text{Total Contribution Margin}}{\text{Total Revenue}}$

For example, if the price is $10 and the unit variable cost is$2, then the unit contribution margin is $8, and the contribution margin ratio is$8/10 = 80%. Profit and Loss as Contribution minus Fixed Costs. Contribution margin can be thought of as the fraction of sales that contributes to the offset of fixed costs. Alternatively, unit contribution margin is the amount each unit sale adds to profit: it is the slope of the profit line. Cost-Volume-Profit Analysis (CVP): assuming the linear CVP model, the computation of Profit and Loss (Net Income) reduces as follows: \begin{align} \text{PL} &= \text{TR} - \text{TC}\\ &= \left(\text{C}+\text{V}\right)\times \text{X} - \left(\text{TFC} + \text{V} \times \text{X}\right)\\ &= \text{C} \times \text{X} - \text{TFC} \end{align} where TC = TFC + TVC is Total Cost = Total Fixed Cost + Total Variable Cost and X is Number of Units. Thus Profit is Unit Contribution times Number of Units, minus the Total Fixed Costs. The above formula is derived as follows: From the perspective of the matching principle, one breaks down the revenue from a given sale into a part to cover the Unit Variable Cost, and a part to offset against the Total Fixed Costs. Breaking down Total Costs as: $\text{TC} = \text{TFC} + \text{V} \times \text{X}$ one breaks down Total Revenue as: \begin{align} \text{TR} &= \text{P} \times \text{X}\\ &= \bigl(\left(\text{P} - \text{V} \right)+\text{V}\bigr)\times \text{X}\\ &= \left(\text{C}+\text{V}\right)\times \text{X}\\ &= \text{C}\times\text{X} + \text{V}\times \text{X} \end{align} Thus the Total Variable Costs $\text{TVC} = \text{V} \times \text{X}$ offset, and the Net Income (Profit and Loss) is Total Contribution Margin minus Total Fixed Costs: \begin{align} \text{PL} &= \text{TR} - \text{TC}\\ &= \left(\text{C}+\text{V}\right)\times \text{X} - \left(\text{TFC} + \text{V} \times \text{X}\right)\\ &= \text{C} \times \text{X} - \text{TFC}\\ &= \text{TCM} - \text{TFC} \end{align} ## Examples  Sales 462,452 Less Variable Costs: Cost of Goods Sold Sales Commissions Delivery Charges $230,934$ 58,852 $13,984 Total Variable Costs$ 303,770 Contribution Margin (34%) $158,682 Less Fixed Costs: AdvertisingDepreciationInsurancePayroll Taxes RentUtilitiesWages$ 1,850 $13,250$ 5,400 $8,200$ 9,600 $17,801$ 40,000 Total Fixed Costs $96,101 Net Operating Income$ 62,581

The Beta Company's contribution margin for the year was 34 percent. This means that, for every dollar of sales, after the costs that were directly related to the sales were subtracted, 34 cents remained to contribute toward paying for the indirect (fixed) costs and later for profit.

Contribution format income statements can be drawn up with data from more than one year's income statements, when a person is interested in tracking contribution margins over time. Perhaps even more usefully, they can be drawn up for each product line or service. Here's an example, showing a breakdown of Beta's three main product lines.

Line ALine BLine C
Sales$120,400$202,050$140,002 Less Variable Costs: Cost of Goods Sold$70,030$100,900$60,004
Sales Commissions$18,802$40,050$0 Delivery Charges$ 900$8,084$ 5,000
Total Variable Costs$89,732$ 149,034$65,004 Contribution Margin$ 30,668$53,016$ 74,998
percentage25%26%54%

Although this shows only the top half of the contribution format income statement, it's immediately apparent that Product Line C is Beta's most profitable one, even though Beta gets more sales revenue from Line B (which is also an example of what is called Partial Contribution Margin - an income statement that references only variable costs). It appears that Beta would do well by emphasizing Line C in its product mix. Moreover, the statement indicates that perhaps prices for line A and line B products are too low. This is information that can't be gleaned from the regular income statements that an accountant routinely draws up each period.

### Contribution margin as a measure of efficiency in the operating room

The following discussion focuses on Contribution Margin (mean) per operating room hour in the operating room and how it relates to operating room efficiency.

FIGURE: Metric Measure for OR Efficiency[2]

Metric Measures012
Excess Staffing Costs>10%5-10%<5%
Start-time tardiness (mean tardiness for elective cases/day)>60 min45-60 min<45 min
Case cancellation rate>10%5-10%<5%
Post Anesthesia Care Unit (PACU) admission delays (% workdays with at least one delay in PACU admission)>20%10-20%<10%
Contribution Margin (mean) per operating room hour<$1,000/hr$1–2,000/hr>\$2,000/hr
Operating Room Turnover Time (mean setup and cleanup turnover times for all cases)>40 min25-40 min<25 min
Prediction Bias (bias in case duration estimates per 8 hours of operating room time)>15 min5-15 min<5 min
Prolonged turnovers (%turnovers > 60 min)>25%10-25%<10%

A surgical suite can schedule itself efficiently but fail to have a positive contribution margin if many surgeons are slow, use too many instruments or expensive implants, etc. These are all measured by the contribution margin per OR hr. The contribution margin per hour of OR time is the hospital revenue generated by a surgical case, less all the hospitalization variable labor and supply costs. Variable costs, such as implants, vary directly with the volume of cases performed.

This is because fee-for-service hospitals have a positive contribution margin for almost all elective cases mostly due to a large percentage of OR costs being fixed. For USA hospitals not on a fixed annual budget, contribution margin per OR hour averages one to two thousand USD per OR hour.

## References

1. ^ a b Farris, Paul W.; Neil T. Bendle; Phillip E. Pfeifer; David J. Reibstein (2010). Marketing Metrics: The Definitive Guide to Measuring Marketing Performance. Upper Saddle River, New Jersey: Pearson Education, Inc. ISBN 0-13-705829-2. The Marketing Accountability Standards Board (MASB) endorses the definitions, purposes, and constructs of classes of measures that appear in Marketing Metrics as part of its ongoing Common Language: Marketing Activities and Metrics Project.
2. ^ Macario, A. "Are Your Hospital Operating Rooms "Efficient"?" Anesthesiology 2006; 105:237-40.