Customer Concentration Risk Calculator
How much of your business rides on a handful of customers? Enter your total revenue and your top five customers, and this tool shows your single-customer, top-three and top-five concentration, with a plain risk band. It is the number a buyer looks at first. Nothing you enter is stored.
Last updated August 30, 2026
How it works
Concentration is simply each customer's revenue as a share of your total. The single largest customer matters most, because losing it is the sharpest shock. Buyers care about this more than almost any other operating number, because a business that depends on one or two accounts is fragile, and fragility lowers both resilience and price. Recurring, contracted revenue is the counterweight: a large customer on a multi-year contract is very different from a large customer who could leave next quarter.
A worked example
Say a business does $2,000,000 in revenue, and its top five customers are $600,000, $300,000, $200,000, $150,000 and $100,000. The largest customer is 30 percent of revenue, the top three are 55 percent, and the top five are 67.5 percent. A single customer at 30 percent lands in the elevated band: real risk, the kind a buyer will discount for unless it is locked in by contract.
I learned this the hard way. A large part of my own company's early revenue once sat with a single account, and I have written about what that felt like when it wobbled, in The Things I Never Told Anyone.
Reading the bands
Under 10 percent is low concentration and the most resilient. Ten to twenty percent is moderate and worth watching. Twenty to thirty-five percent is elevated, a real risk that buyers discount for. Above thirty-five percent is high: one customer is a large share of the business, and derisking it, usually through diversification or contracted recurring revenue, is one of the highest-return things an owner can do before a sale.
Related tools and reading
Frequently asked questions
Why does one big customer lower the value of a business?
Because it is a risk a buyer inherits. If a single customer is a large share of revenue and leaves, the earnings the buyer paid for disappear. Buyers price that risk in, and recurring or contracted revenue is the main thing that offsets it.
What counts as a customer here?
Whatever unit bills and could leave independently. If one parent company owns several accounts that would all go together, treat them as one customer, because that is how the risk actually behaves.
What is a safe level of concentration?
There is no single safe number, but the lower the better. Under ten percent for your largest customer is comfortable; above a third is a concentration a buyer will focus on. The trend and the contracts matter as much as the level.
Is my data stored?
No. The calculation runs entirely in your browser. Nothing you enter is saved or sent anywhere.