Business valuation calculators
Customer Concentration Calculator
See how much of your revenue depends on your largest customers
In short
Customer concentration is the share of revenue held by your largest customers. Divide each customer's revenue by total revenue, then look at the largest customer and the top three and five combined. Buyers use these percentages to judge how repeatable earnings are, and concentration often changes deal structure before it changes price.
Concentration is one of the first things a buyer measures. This calculator shows how much of your revenue sits with your largest customers and what that exposure looks like from the other side of the table.
Part of the business valuation calculators suite from BusinessValuation.co.uk. Your result is saved in this browser, so you can compare it with your other calculator results.
How to use this calculator
Enter total annual revenue and the revenue generated by your largest customers. The calculator will show how much of the business depends on its top one, three and five customers. You do not need to identify customers by name.
How to read this result
Customer concentration measures how much of your revenue depends on a small number of relationships. Buyers use it to judge how repeatable your earnings are, and it can affect the valuation multiple, buyer appetite, deal structure, whether an earn-out is proposed, the warranties requested and any retention conditions. No automatic valuation discount is applied here, because no defensible universal percentage exists.
Your three most important concentration risks
- Your largest customer represents 30% of revenue, which most buyers treat as a pricing and structuring issue rather than a detail.
- Your top three customers represent 55% of revenue, so the loss of two relationships would change the earnings profile materially.
Areas to investigate before a sale
- Check whether any customers are part of the same group; related companies should be assessed as one economic relationship.
- Gather contract copies, renewal dates, notice periods and any change-of-control clauses.
- Record how long each major relationship has run and which people inside the business own it.
- Review gross margin by customer, because a large customer on thin margin carries a different risk again.
- Build evidence of new-customer wins to show the pipeline does not depend on one account.
Suggested next steps
- Check whether any customers are part of the same group; related companies should be assessed as one economic relationship.
- Gather contract copies, renewal dates, notice periods and any change-of-control clauses.
- Record how long each major relationship has run and which people inside the business own it.
- Review gross margin by customer, because a large customer on thin margin carries a different risk again.
Your concentration position
Largest customer share of revenue
30%
- Largest customer
- 30%
- Top three customers
- 55%
- Top five customers
- 65%
- Top ten entered customers
- 65%
- Concentration category
- High concentration
- Contract position
- Under written contract, about 14 months remaining
- Revenue outside the entered customers
- £840,000
- Revenue exposed if the largest customer is lost
- £720,000
- Revenue exposed if the top three are lost
- £1,320,000
Before you rely on this
- Concentration does not produce a fixed valuation discount. There is no defensible universal percentage, so no automatic reduction is applied here.
- Companies in the same group should be assessed as one economic relationship, even where they invoice separately.
Next steps
Your result is above and stays visible. Ask us how buyers may assess your customer concentration.
Important information
This calculator provides general, indicative guidance based solely on the information entered. It is not a formal business valuation, tax calculation, legal opinion or recommendation to accept or reject an offer. Actual value and sale proceeds depend on detailed financial, commercial and transaction-specific factors.
How this calculation works
- Customer share = customer revenue ÷ total revenue
- Top three concentration = sum of the three largest customer shares
- Top five concentration = sum of the five largest customer shares
- Revenue at risk if the largest customer leaves = largest customer revenue × gross margin
Worked example: £4m revenue business
| Total revenue | £4,000,000 |
|---|---|
| Largest customer | £1,200,000 (30%) |
| Second customer | £560,000 (14%) |
| Third customer | £400,000 (10%) |
| Top three concentration | 54% |
| Remaining customers | 46% |
At 30% in one relationship and 54% in three, a buyer will test contract length, change-of-control terms, tenure and profitability per account. Structure, warranties and retention terms are usually where this shows up first.
What each input means
- Total annual revenue
- Revenue for the most recent full year, or annualised.
- Largest customers
- Revenue for each significant relationship, grouped where one group owns several entities.
- Contract basis
- Whether the revenue is contracted with a term and notice period, repeat but uncommitted, or project by project.
How to read the result
The percentages show how dependent earnings are on a few relationships. No automatic valuation discount is applied, because no defensible universal percentage exists. Treat the result as a risk position to evidence and manage, not a deduction from value.
What can materially change the result
- Contract length, notice periods and change-of-control clauses.
- How long each large customer has been with you and at what margin.
- Whether the relationship sits with the owner or with the business.
- Whether the customer is itself concentrated or cyclical.
- Whether new customer wins are reducing the largest share over time.
Limitations
- It does not apply a valuation discount or produce a multiple.
- It does not assess customer credit quality.
- It does not weight profitability by customer unless you enter margin separately.
When this calculator is appropriate
Use it when preparing for a sale, an investment or a valuation, and when planning how to reduce dependency over the next one to three years.
When it is not appropriate
Do not use it as the concentration disclosure in a formal report or information memorandum without underlying customer-level evidence.
Bottom line
Concentration is priced through structure as much as through multiple. Contracted, long-tenured, profitable large customers are a different risk from uncontracted ones.
Questions owners ask
- What is customer concentration?
- Customer concentration measures how much of your revenue depends on a small number of customers. It is usually expressed as the percentage of annual revenue represented by the largest customer, and by the top three and top five combined.
- What percentage from one customer is considered high?
- Above 40 per cent is treated as severe, 25 to 40 per cent as high, 15 to 25 per cent as material and 10 to 15 per cent as moderate. Below 10 per cent is generally regarded as diversified.
- Why does concentration affect business value?
- Because it affects the reliability of future earnings. A buyer paying a multiple of profit is buying repeatability, and a single relationship that could end changes the risk they are taking.
- Do written contracts remove concentration risk?
- No. Contracts help, but the notice period, remaining term, change-of-control provisions and the commercial relationship behind them matter more than the existence of a signed document.
- Should related companies be treated as one customer?
- Yes. If several customers sit in the same group or share the same decision maker, a buyer will combine them, because one decision could remove all of that revenue.
- Can customer concentration lead to an earn-out?
- It often does. Where a buyer cannot be confident the largest relationships will continue, they commonly propose deferred consideration or an earn-out linked to retention.
- How can a business reduce concentration before sale?
- By winning new customers in the same segment, contracting the existing large relationships on longer terms, moving relationships from the owner to the team, and evidencing a pipeline that does not rely on one account.
- Is this a valuation discount calculation?
- No. It measures exposure and explains how buyers respond to it. It does not apply a discount, because no reliable universal percentage exists.
Related reading
Free business valuation
We assess how your concentration position is likely to be read by buyers, and what evidence reduces the perceived risk.
Where owners usually go next
- Recurring Revenue Calculator
Test how much of the revenue behind those customers is genuinely contracted.
- Exit Readiness Score
See where concentration sits among the other areas buyers test.
Written and reviewed by Tony Vaughan, founder and lead adviser, BusinessValuation.co.uk.·Last reviewed: September 2026·How we produce these figures
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