Customer Concentration Calculator

Measure how much revenue depends on your biggest customers and what losing one would do to runway. The result updates as you type so you can compare scenarios quickly.

The method

How it is worked out

Concentration = largest customer ÷ revenue; runway after loss = cash ÷ (burn + lost gross profit ÷ 12)
gross profit at risk
Lost revenue × gross margin; costs rarely fall as fast as revenue

Keep in mind

What it leaves out

  • Contract termsNotice periods and minimums soften the hit.
  • PipelineReplacements in late-stage pipeline are not counted.

Use the calculator to compare scenarios rather than as a guaranteed forecast.

About the Customer Concentration Calculator

Measure how much of your revenue rests on your largest customers and what losing one would do to runway.

How it works and an example to tryShow less

How to use the result

Top-customer shares are divided by revenue. Gross profit at risk is the largest customer times gross margin, monthly. Runway after loss divides cash by burn plus that lost gross profit.

Example to try

A £3m business with a £600k top customer has 20% concentration. Losing it removes £37,500 of gross profit a month, cutting runway from 25 to 15 months.

Put it to work

Try it on a real situation

Load an example

What moves the result most

    Worked out from your figures above. Tap a row to try it.

    Who uses it, and when

    Founders, CFOs and anyone preparing for a fundraise, loan or acquisition.

    Mistakes worth avoiding

    • Celebrating a big logo without a multi-year contract.
    • Modelling the loss as revenue only, when costs stay.
    • Ignoring concentration by channel or reseller.

    Questions

    What does the Customer Concentration Calculator do?

    Measure how much revenue depends on your biggest customers and what losing one would do to runway.

    How should I use the result?

    Top-customer shares are divided by revenue. Gross profit at risk is the largest customer times gross margin, monthly. Runway after loss divides cash by burn plus that lost gross profit.

    Does TechBullion store the information I enter?

    The core calculation or transformation runs in your browser. Normal website security and analytics may still record page-level events, but the tool does not need to create a public record from your inputs.

    What mistakes do people make with a customer concentration calculator?

    Celebrating a big logo without a multi-year contract. Modelling the loss as revenue only, when costs stay. Ignoring concentration by channel or reseller.

    Is the result guaranteed?

    No. Use the result as a practical check or planning aid and verify important decisions with the relevant primary source, provider or professional advice.

    Part of the guide · Cash and runway · 15 tools

    Startup fundraising and equity

    Valuation methods, SAFE and convertible note conversion, cap tables, dilution, option pools, liquidation preferences, burn rate and runway.

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    Burn Rate CalculatorRunway Calculator13-Week Cash Flow Forecast
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    Results are estimates based on the figures entered, for general information only, and not financial, investment, tax or legal advice. See our terms of use.