The whole calculation, in one line
Missed calls per week, times your booking rate on the calls you do answer, times your average job value, times fifty-two.
That is it. The rest of this guide is about getting each of those four numbers honestly, because the arithmetic is trivial and the inputs are where every estimate goes wrong.
Work it weekly rather than monthly. Call volume in the trades moves with weather and season, and a monthly figure hides the week that actually hurt you.
The short versionMissed calls per week x booking rate x average job value x 52. Everything else is getting the inputs right.
1. Missed calls per week: your phone system already knows
This is the one number you do not have to estimate, and almost nobody looks it up. Every VoIP system, mobile carrier account and call-tracking tool records unanswered and abandoned calls. Pull the last thirteen weeks rather than the last one, so a quiet week does not flatter you.
Count three things separately, because they are different problems: calls that rang out with nobody there, calls that were answered by voicemail, and calls that hung up while on hold. The third group is the most annoying to discover, because those people did reach you.
If your system does not report this, that is itself the finding. You are running a business whose main intake channel is unmeasured.
The short versionPull thirteen weeks, and separate rang-out from voicemail from abandoned-on-hold.
2. Booking rate: measure it on answered calls only
Of the calls you do answer, what share becomes a booked job? Your scheduling software or CRM can usually tell you, and if it cannot, a fortnight of tallying on paper will.
Apply that same rate to the missed calls. This is the assumption doing the most work in the whole calculation, and it is worth being explicit that it is an assumption: a caller who could not reach you was not necessarily a caller who would have booked.
It cuts the other way too, though. People ring a contractor when something is wrong, not to browse. The intent behind an inbound trade call is higher than almost any other channel you pay for.
The short versionUse your real answered-call booking rate, and be honest that applying it to missed calls is an assumption.
3. Average job value: use the median, not the mean
One equipment replacement in a year of service calls will drag a mean upward and make your estimate look better than reality. The median job, the one in the middle, is the honest figure for this purpose.
If you want the fuller number, add the value of the second job rather than the first. A customer acquired through a service call who later replaces a system is worth considerably more than the call that introduced them, and that is the real reason missed calls hurt: you are not losing one job, you are losing the relationship that would have produced the next four.
Run it both ways. The gap between the two answers tells you how much of your business is repeat work, which is useful to know regardless.
The short versionMedian job value for the conservative number, lifetime value for the real one.
4. The number this arithmetic cannot see
Everything above counts jobs. It does not count what a missed call does to your reputation, and in a trade where most work arrives by recommendation, that is not a rounding error.
A customer who could not reach you during a failure does not usually complain. They tell the next person who asks them for a recommendation, and you never learn that the conversation happened. There is no report that shows this and no honest way to put a figure on it, so we are naming it rather than pretending to quantify it.
The same applies in reverse. Answering at eleven at night when the competition did not is the thing people actually remember and repeat.
The short versionThe referral you never hear about is real and unmeasurable. Do not let the spreadsheet convince you it is zero.
Why after-hours is a different calculation entirely
A call missed at two in the afternoon might be recovered. The caller may leave a message, or ring again, because it is a normal hour and they assume you are busy.
A call missed at two in the morning behaves differently. The person calling has a failure right now, usually a heating or cooling system in weather that makes it urgent, and they are working down a list of numbers. Whoever answers gets the job. There is no second position on that list.
This is why voicemail performs so badly out of hours specifically. It is not that voicemail is useless; it is that its usefulness collapses exactly when the calls are most valuable and most urgent.
The short versionWeight after-hours misses higher than daytime ones. They convert differently because the caller behaves differently.
What to do with the number once you have it
Compare it against the cost of the thing that would fix it, and be fair in the comparison. An after-hours rota, an answering service and an AI agent all have running costs, and all three beat voicemail.
If the annual figure is smaller than the cheapest fix, you have learned something genuinely useful and should stop here. That happens, particularly for businesses with low call volume and high job values, where the owner picking up personally is simply the right answer.
If it is several times larger, you have a number to take into that decision instead of a feeling. That was the point of doing the arithmetic.
The short versionThe calculation is worth doing even when it tells you to do nothing. Especially then.
