Most freelancers track their income, not its shape. You can be fully booked and still be one lost contract away from a bad quarter if a single client is quietly propping up your whole business. This calculator takes your total monthly revenue and your biggest client's share of it, and turns that into a concrete risk read — plus the dollar ceiling that keeps you diversified instead of dependent.
How it works
You enter two numbers: your total monthly revenue across every client, and what your single largest client pays you in that same month. The calculator divides the second by the first to get your concentration percentage — the share of your income that rides on one relationship.
That percentage sorts into three bands. Under 15% is healthy: no one client can sink you. Between 15% and 25% is caution: manageable, but worth watching and actively working to dilute. Above 25% is high risk: more than a quarter of your income depends on one client staying happy, staying in business, and staying your client — none of which you fully control.
Alongside the risk read, you get two plain-dollar numbers: how much monthly income disappears the moment that client leaves, and what 15% of your current revenue works out to — a rough ceiling for what any one client should be worth to you if you want to stay in the healthy band.
Worked example
Say your total monthly revenue is $8,000, and your biggest client accounts for $3,000 of that.
- Concentration: $3,000 ÷ $8,000 × 100 = 37.5%
- Risk level: 37.5% is above 25% → High risk
- Monthly income at risk: $3,000 — gone the day that client walks
- Healthy max per client: 15% of $8,000 = $1,200
That last number is the useful one. It's not telling you to fire your best client or cap what they pay you — it's telling you that for this client to stop being a single point of failure, everything else you bill needs to grow until $3,000 is 15% of the total, not 37.5% of it. At your current revenue, that means roughly doubling your non-this-client income, or landing two or three more accounts around $1,000-$1,500 a month each.
How to interpret your result
A high concentration number isn't a verdict on the client — it's a statement about your business structure. The client did nothing wrong by giving you a lot of work; the risk exists because you built revenue architecture with one load-bearing wall. If they cut budget, get acquired, hire in-house, or just go quiet for two months, your income doesn't dip, it craters.
Caution-band freelancers (15-25%) are usually fine in the short term but should treat every slow week with that client as prospecting time, not downtime. High-risk freelancers (25%+) should be actively pitching new work even — especially — when the big client is keeping them fully booked, because "too busy to prospect" is exactly how concentration risk becomes permanent.
The honest caveat: this number alone doesn't tell you how likely that client is to leave. A 30%-of-revenue client on a five-year retainer with a happy, stable company is a different risk than a 20%-of-revenue client who mentioned their VP just left. Use the percentage as a structural warning light, not a precise probability — pair it with what you actually know about the relationship.
Methodology & sources
The formula is concentrationPercent = round2(largestClientRevenue ÷ totalMonthlyRevenue × 100), with monthlyIncomeAtRisk = largestClientRevenue and healthyMaxPerClient = round2(totalMonthlyRevenue × 0.15). The risk band is under 15% = Healthy, 15-25% = Caution, over 25% = High risk. All outputs are rounded from unrounded intermediate math so the numbers stay internally consistent.
The 15%/25% bands used here echo the concentration thresholds finance and accounting tools apply to small businesses more broadly — FreeAgent's guide to customer concentration risk notes that its own risk-alert system flags accounts once a single customer reaches 25% of revenue over a rolling period, and cites the commonly used investor guideline that any one customer above roughly 10% of revenue starts to warrant scrutiny. Neither figure is a legal or accounting standard — there's no regulator setting a bright line for freelancers — but they're a reasonable, widely used starting point for deciding when "a great client" has quietly become "a dependency."