Enter revenue for your top customers to get an HHI concentration score plus top-1 and top-3 share, so you can see how exposed your business is to any single account.
Enter annual revenue for your five biggest customers, plus everyone else combined. Leave any field blank if it does not apply.
A score above 2,500 is generally read as highly concentrated. Your top customer alone makes up 42.0% of tracked revenue.
Built by Rankite, the SEO team behind Swordfish AI's +400% revenue and Zluri's +45% organic growth. See the case studies
Customer concentration is how much of your revenue depends on a small number of accounts. A business with 200 customers each worth roughly the same amount can lose one and barely notice. A business where one customer accounts for 40% of revenue is in a very different position: that single relationship ending, or even just renegotiating harder, can reshape the whole year. This calculator turns a list of customer revenue figures into two things: a concentration score called the Herfindahl-Hirschman Index (HHI), and simple top-1 and top-3 share percentages.
The HHI is calculated by squaring each customer's percentage share of total revenue and adding the squares together. Squaring matters because it punishes big shares far more than small ones: a single customer at 50% contributes 2,500 points to the score on its own, while ten customers evenly split at 10% each contribute only 1,000 points combined, even though both scenarios total 100% of revenue. This scoring convention is borrowed from antitrust market analysis, where regulators use the same bands to judge how concentrated an industry is: under 1,500 is considered unconcentrated, 1,500 to 2,500 is moderate, and above 2,500 is considered highly concentrated. Applied to a single company's customer base instead of a whole market, it works as a quick, comparable diversification score you can track over time.
A high concentration score is not automatically a crisis, especially for a young company still landing its first few accounts. But it is worth treating as a flag: lenders and investors often look harder at any single customer worth more than 10% to 15% of revenue, and a renewal conversation with that account carries outsized weight. If your score is high, the practical response is usually to keep serving the big accounts well while deliberately investing in new customer acquisition, so growth in the smaller accounts dilutes the concentration over time rather than trying to shrink the big relationships on purpose.
Work out how fast you're losing customers or revenue.
Estimate what an average customer is worth over their lifetime.
See how much revenue you kept and grew from existing customers.
Get a free, no-obligation SEO audit and a 30-minute strategy session. We'll show you exactly where the growth is hiding.
Fill out the form and we'll get back to you within one business day. Prefer email? Write to us directly at contact@rankite.com.