Every article about missed calls quotes somebody else's average. This one doesn't. Grab your phone system's call log — or a notepad and one honest week — and compute your number. The math takes five minutes, and it uses only inputs you can verify yourself.
For calibration, two baseline stats worth knowing before you start: roughly 62% of small-business calls go unanswered (Aira), and 85% of callers who reach voicemail never call back (Aira). Your numbers may be better. They may be worse. That's the point of counting.
One thing to hold while you read: the missed call is the leak you can hear, but it's a symptom, not the disease. What actually moves revenue is the whole machine behind the phone — capture, booking, follow-up, reviews, reactivation, reporting — running as one system instead of six tools and your own memory. This article covers the audible part; the fix worth pricing is the machine.
Step 1: Count the calls that ring out
Not the calls you think you miss — the ones you actually do. Pull one week from your phone system, or tally by hand. Count every call that went to voicemail or rang out during business hours, plus everything that came in after hours. Call this A (missed calls per week).
If you can't measure yet, the 62% figure above says the honest default for a busy small business is "more than you'd guess." But measure. Guessing is how this problem stays invisible.
Step 2: Estimate how many were new business
Some ring-outs are vendors, robocalls, or existing customers who'll call back. Be conservative: listen to the voicemails you did get, look at the callback numbers, and estimate the fraction that were potential new customers. Call this B (a decimal — if 4 of 10 missed calls look like new business, B = 0.4). When unsure, round down.
Step 3: Write down your average job or client value
This is your number, not an industry average. What does a typical new customer spend — on the first job, or over the relationship if repeat business is your model? Pick one basis and stay consistent. Call this C.
Step 4: Apply a conservative close rate
Not every answered call becomes a customer. What fraction of new-business callers do you actually win when you do answer? If you don't track it, use something deliberately modest — 25% is a defensible floor for most service businesses. Call this D.
The formula
Weekly leak = A × B × C × D. Multiply by 50 for the annual number.
The 85% stat is why the leak is nearly total: more than four in five callers who hit voicemail never call back, so a missed new-business call and a lost one are almost the same thing. If you want to be strict, multiply the result by 0.85 — the outcome will not change your decision.
Two worked examples (both hypothetical)
A hypothetical plumber whose average job is $400. Suppose she misses 10 calls a week (A = 10), estimates 4 in 10 are new business (B = 0.4), and closes 30% of the calls she answers (D = 0.3). Weekly leak: 10 × 0.4 × 400 × 0.3 = $480 a week — roughly $24,000 a year. These are made-up inputs to show the arithmetic, not a client result; her real log might say 6 calls or 16.
A hypothetical dental practice. Say the front desk misses 8 calls a week (A = 8), 1 in 4 is a prospective new patient (B = 0.25), lifetime value per new patient is $850 (C), and half of answered new-patient calls book (D = 0.5). Weekly leak: 8 × 0.25 × 850 × 0.5 = $850 a week — about $42,500 a year in lifetime value. Again: illustrative inputs, deliberately conservative. Yours will differ.
When your number says "don't bother"
Run the math honestly and sometimes it clears you. If A is small because someone genuinely dedicated answers your phone all day, you don't have this problem. If you're booked out for weeks and want the phone to throttle demand, a missed call is a filter, not a leak. And if your leak is downstream — no-shows, unclosed quotes — fix that first. The calculator's job is to tell you the truth, including the boring version.
But if the weekly number made you wince, the fix isn't answering harder — you already would if you could. It's a layer that answers every call, books real appointments, and only interrupts you when it matters. If you want to see what that looks like against your own numbers, book a walkthrough and bring the worksheet.
Book a 15-minute walkthrough — or call (626) 365-4946 and hear it answer for yourself; yes, an AI picks up, and that's the point.