What it means
The calculation is straightforward: take the revenue from your biggest customer, or your top five or ten, and divide it by total revenue for the same period. The result describes how evenly your income is spread.
A business earning $12m across 400 customers is in a very different position from one earning $12m where a single client provides $6m. It matters because concentration is a form of hidden leverage on the whole business.
A concentrated customer base often comes with better margins and lower selling costs, but it also hands significant pricing power to the customer and turns one contract renewal into an existential event. Lenders frequently write concentration limits into loan covenants for exactly this reason.
The metric is used most sharply in company sales and fundraising. Acquirers routinely discount the valuation of a business where one customer exceeds 20% to 25% of revenue, or structure part of the price as an earn-out contingent on that customer staying.
Founders who intend to sell within a few years often start deliberately diversifying long before they go to market. There are important nuances beyond the headline percentage.
Concentration by profit can differ sharply from concentration by revenue if the big customer is heavily discounted, and concentration by ultimate parent matters more than by trading entity, since several separately invoiced subsidiaries can belong to the same group. Contract length, switching costs and relationship depth all change how dangerous a given percentage really is.
Concentration cuts both ways in accounting terms too. Accounting standards generally require disclosure of major customers that exceed 10% of revenue in the financial statements, so the risk is visible to anyone who reads the notes rather than something a management team can quietly ignore.
In practice
Real-world examples.
Example
A contract manufacturer generates 55% of revenue from one consumer electronics brand. When that brand moves production to a competitor, the manufacturer has to make a third of its workforce redundant within six months, despite having been profitable and growing the previous year.
Example
A marketing agency preparing for sale discovers its top client represents 34% of fee income. The owners spend two years deliberately winning smaller accounts, bringing the figure to 18%, and the eventual sale price reflects a noticeably lower risk discount.
Example
A logistics business applies for a $4m expansion facility. The bank sets a covenant requiring that no single customer exceed 25% of revenue, forcing the finance director to report concentration monthly rather than only at year end.
Think of it
“Concentration shows how dependent you are on big customers-revenue spread across customer base.
Formula
Calculation
Customer Concentration = (Revenue from Customer or Customer Group / Total Revenue) x 100
An engineering services firm reports total annual revenue of $12,000,000. Its largest client, a national infrastructure operator, contributed $3,600,000. The next four largest clients contributed $3,600,000 between them.
Top customer concentration = ($3,600,000 / $12,000,000) x 100 = 30%
Top five concentration = (($3,600,000 + $3,600,000) / $12,000,000) x 100 = ($7,200,000 / $12,000,000) x 100 = 60%
So three tenths of the business rests on one relationship and three fifths on five. If the largest client left and could not be replaced within the year, revenue would fall to $8,400,000, and because most overheads are fixed in the short run, the profit impact would be far more severe than the 30% revenue figure suggests.Case study
Seen in the real world.
This is an illustrative and entirely fictional example. Cedarcroft Packaging, an invented supplier of moulded packaging, grew comfortably for six years on the back of one large food producer that accounted for 48% of its sales. Margins on that account were thin but volumes were predictable, and the management team saw the relationship as a strength rather than a risk.
When the food producer was acquired, the new parent consolidated packaging suppliers and gave Cedarcroft twelve months' notice. The team had a year to replace nearly half its revenue, which was not enough time, and the business had to close one of its two production lines and renegotiate its bank facility.
In the illustrative aftermath, Cedarcroft rebuilt with a rule that no customer would be allowed to exceed 20% of revenue, even if that meant declining volume. Growth was slower for three years, but the business survived the loss of its next largest customer without drama, which was precisely the point.
Watch out
Common mistakes.
- Measuring concentration by legal entity rather than by ultimate parent. Five subsidiaries that each look like 8% of revenue can be one group representing 40% of your risk.
- Looking only at revenue concentration. A customer taking 30% of revenue but 55% of gross profit is a far bigger exposure than the revenue figure implies.
- Assuming a long contract removes the risk. Contracts can be renegotiated, breached or simply not renewed, and a large customer usually has more negotiating power than the supplier does.
Questions
People also ask.
What level of customer concentration is considered risky?
There is no fixed line, but many acquirers and lenders start asking hard questions above 20% for a single customer, and treat anything above 30% as a material risk needing mitigation.
Does high concentration always destroy value?
Not always, since deep integration, long contracts and high switching costs can make a concentrated relationship durable, but buyers will still price in the possibility that it ends.
How can a business reduce concentration quickly?
Genuinely quick fixes are rare, so the practical routes are growing the rest of the base faster than the large account, entering an adjacent market, or acquiring a business with a different customer set.
From the founder's library
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