The usual version of this math is one multiplication. Average ticket times calls missed. Say a plumber charges 480 dollars a job, misses eight calls a week, and works out that he's setting 3,840 dollars on fire every seven days. That number is wrong, and wrong in a direction that hides something useful: the guy quoting 14,000 dollar roof replacements loses less per missed call than the woman washing dogs out of a van.

Four businesses follow and none of them exist. I made up every margin, every close rate, every dollar. Sketches shaped like real trades. Delete my numbers, write in yours.

The five numbers, and the one everybody skips

Treat your average ticket as the cost of a missed call and you've skipped four steps. A ringing phone is a lottery ticket with four odds stacked in front of it, and then a fifth number almost nobody applies.

  • How many inbound calls are actually prospects. Suppliers, subs, wrong numbers, a customer asking where the invoice went, and eleven robocalls about your vehicle's extended warranty all ring the same phone.
  • How often you close when you do pick up.
  • Contribution margin, not revenue. What's left after the parts and the hours that specific job ate. Leave overhead out of it, because the rent gets paid whether the phone rings or not.
  • What that customer is worth after the first job, averaged across the ones who stay and the ones you never hear from again.
  • The odds they're gone for good. The Numa Small Business Phone Report found that 85 percent of callers who reach voicemail never call back, so call it 0.85.

The plumber, who started this

Six of every ten calls to his line are real work. When he picks up and can be there before dinner he books seven out of ten, because a man standing in two inches of water isn't shopping around. Ticket's 480, contribution margin about 45 percent, so 216 dollars. Roughly a third of those customers call him again inside two years, a water heater or a hose bib that split in February, which pushes lifetime contribution to something like 300.

0.6 times 0.7 times 300 is 126. Times 0.85 is 107.

One missed call, 107 dollars. Not 480. But he runs two trucks and takes about 60 calls a week, and he's probably missing a quarter of them: after hours, mid crawlspace, both hands on a wrench. Fifteen calls. Call it 1,600 dollars a week. Wrong about the per call figure. Right that it's serious money.

The groomer, who breaks the pattern

Mobile grooming, one van, one person, 85 dollars a dog. She is the labour, so after shampoo, water, fuel and wear she keeps about 60 of it. One dog, one wash, 60 dollars. Sounds like a rounding error.

Except grooming is a subscription nobody calls a subscription. A dog that sticks comes back every six weeks for years. Blend the regulars with the people who book once and vanish and a new caller is worth maybe 14 visits, so 840 dollars of contribution. Half her calls are new client inquiries. She books half of those, because Tuesdays are full and some people only wanted a price.

0.5 times 0.5 times 840 is 210. Times 0.85 is 178.

She's also the worst placed person here to answer a phone. Wet hands, clippers running, and a spaniel on the table who will absolutely jump.

The roofer, whose big number is lying to him

Full tear off and replacement runs 14,000 dollars. Margin 25 percent, so 3,500 of contribution. Thirty times the plumber's ticket, a hundred and sixty times a dog wash. It barely matters. Look at the funnel.

Just over half his inbound calls are homeowners at all. The rest are suppliers, subs, adjusters, and people who want a free bid to wave at the contractor they already chose last Thursday. Of the real ones, 60 percent let him up on the roof. Of those inspections, one in five turns into work.

0.55 times 0.6 times 0.2 times 3,500 is 231. Times 0.85 is 196.

So a 14,000 dollar roof and an 85 dollar bath on a labradoodle land within twenty dollars of each other. And he gets no second bite. He re-roofs that house in 2050, if he's still climbing ladders and she hasn't moved to Arizona.

The mechanic, and the multiplier that gets abused

An independent shop with three bays. Average repair order 420 dollars, margin around 48 percent, so 202. This is where people cheat. They picture the loyal customer with nine repair orders over four years, multiply 202 by nine, get 1,818 and announce that every missed call costs the shop a mortgage payment.

Don't. Most first timers are one and done. Average across everyone who has ever pushed that door open and four visits is closer to honest, so 808 dollars. Say 65 percent of his calls are real prospects and he books 60 percent of those.

0.65 times 0.6 times 808 is 315. Times 0.85 is 268.

Least dramatic job on the list, most expensive silence. Retention does that.

Where this arithmetic falls apart

Annualising it. The groomer can't wash 40 dogs a week however fast she answers, so once her calendar's full a missed call costs her the gap between the dog she got and the dog she'd rather have had. The plumber's weekly figure holds right up until it turns into a third truck and a hiring problem. Any sales rep who hands you a 200,000 dollar annual number has multiplied straight past your own capacity and is betting you won't check it against your own diary.

Use the per call number as a spending limit instead. It tells you what answering is worth to you specifically, which is the only version of this that survives contact with a bank account. A 411 Locals study of 85 businesses found that 62 percent of calls to small businesses go unanswered, which suggests most owners have never worked their limit out at all.

Rocketship's AI receptionist answers on your own number, knows your hours, services and prices, and books into Google Calendar while you're flat on your back under a sink. Free tier, paid plans from 12 dollars a month. One recovered call buys the mechanic almost two years of it. The groomer, about fifteen months.

Work out your own five numbers tonight, on paper, honestly. If the answer comes back 40 dollars, ignore every phone system anyone has ever tried to sell you. If it comes back 268, you've been funding somebody else's truck payment for years and never once seen the invoice.