What it means
This technique is also called vertical analysis, because you read down a single statement measuring each line against one common denominator. It is one of the few analytical tools that requires no assumptions, no forecasts and no adjustments, just division.
That simplicity is exactly why it is the first thing many analysts do with a new set of accounts. The business value is comparability.
Two companies can have identical percentage structures and wildly different revenue, or identical revenue and completely different structures, and the common size view separates the two questions. It lets a $12,000,000 business benchmark itself against a listed peer without the scale difference drowning the signal.
In practice you build it as an extra column beside the dollar column, for each of three to five years. Then you read across for drift.
A gross margin percentage that slides steadily while revenue climbs tells you growth is being bought with discounts, and a rising administrative expense percentage tells you overhead is not scaling with the business. The technique applies to all three primary statements, though it is used most on the income statement and balance sheet.
On the cash flow statement analysts sometimes use revenue or total cash inflows as the base, but there is no single convention, so label whatever base you choose clearly. Being explicit about the denominator prevents most of the misunderstandings that arise in board meetings.
The nuance is that a common size statement shows proportion, not performance. A company can improve every percentage while shrinking, and it can show a stable structure while burning cash.
Pair it with horizontal analysis, which shows growth rates, and with absolute figures before drawing any conclusion.
In practice
Real-world examples
Example 1
A hotel group compares its own income statement in common size form against two listed competitors. Its payroll runs at 38% of revenue against a peer average of 31%, which becomes the single focus of the following year's operating plan.
Example 2
An auditor uses common size statements as a first analytical review before fieldwork. A jump in other operating expenses from 2% to 7% of revenue with no explanation directs the sample selection, and the enquiry uncovers a misclassified capital project.
Example 3
A franchise operator gives every franchisee a common size template so their monthly returns are comparable regardless of outlet size. A small city-centre site and a large out-of-town site can then be judged on the same measure of food cost as a share of sales.
Think of it
Imagine looking at recipe ingredients. A standard financial statement tells you the exact grams of flour, sugar, and butter used by a small bakery or a massive factory. A common size statement converts everything into percentages. Now you can easily see if the factory uses too much butter compared to the bakery, even if they bake vastly different quantities.
Formula
Calculation
Common size percentage = (line item / base figure) x 100, where the base is revenue for the income statement and total assets for the balance sheet
A specialist components business reports revenue of $12,000,000 for the year, cost of goods sold of $7,200,000, operating expenses of $3,000,000 and therefore operating profit of $1,800,000.
Revenue = $12,000,000 / $12,000,000 = 100.0%
Cost of goods sold = $7,200,000 / $12,000,000 = 60.0% of revenue
Gross profit = $12,000,000 - $7,200,000 = $4,800,000, which is $4,800,000 / $12,000,000 = 40.0% of revenue
Operating expenses = $3,000,000 / $12,000,000 = 25.0% of revenue
Operating profit = $4,800,000 - $3,000,000 = $1,800,000, which is $1,800,000 / $12,000,000 = 15.0% of revenue
Checking the structure, 60.0% + 25.0% + 15.0% = 100.0% of revenue, so every dollar of sales is fully accounted for as cost, expense or profit.Case study
Seen in the real world
Petrichor Cleaning Services is an illustrative, fictional commercial cleaning contractor. Over four years its revenue grew from $7,000,000 to $12,000,000, and every monthly board pack led with that growth figure and the fact that operating profit had risen in dollar terms too.
A non-executive director asked for the statements in common size form. Presented that way, the picture changed: cost of delivery had risen from 55% to 60% of revenue and administrative overhead from 20% to 25%, so operating profit had fallen from 25% to 15% of revenue even as the dollar figure grew. The company was buying revenue with contracts priced below its own historical standard.
In this fictional case the board introduced a floor of 35% gross margin on new bids and reviewed the ten largest contracts for repricing at renewal. Revenue growth slowed to single digits the following year, but operating profit in dollars rose faster than it had during the growth phase.
Watch out
Common mistakes
- Using a different base for different lines in the same statement, which makes the percentages impossible to add or compare.
- Reading a common size statement on its own and concluding a business is healthy, when the percentages can look stable while the company shrinks.
- Comparing companies that capitalise costs differently without adjusting, so one shows a lower expense percentage purely because of an accounting policy.
Questions
People also ask
Is a common size financial statement the same as vertical analysis?
Yes, the two terms describe the same technique of expressing each line as a percentage of one base figure within a single statement.
What base should be used for the cash flow statement?
There is no single convention, so most analysts use revenue or total cash inflows and label the choice explicitly on the schedule.
How is it different from horizontal analysis?
Vertical analysis compares lines within one period against a common base, while horizontal analysis compares the same line across periods to show growth rates.