Costs divide into two kinds, and almost everything useful in this piece follows from the split.
Fixed costs arrive whether or not you work: the truck payment, insurance, the phone, the software, the rent on a unit, the accountant. Variable costs arrive per job: materials, fuel for that trip, a subcontractor's day, the card processing fee.
The gap between what a job bills and what it costs in variable terms is the contribution. Contribution is not profit. It is the amount each job hands over toward the fixed pile, and the month turns profitable at the point the pile is covered.
Working it out on real numbers
Add up the fixed costs for one month, honestly, including the ones that arrive annually. An insurance premium of twelve hundred dollars is a hundred a month whether you pay it that way or not.
Then take an average job. Say it bills a thousand dollars and consumes three hundred in materials and fuel. Contribution is seven hundred.
Divide fixed costs by contribution and you have the count. Fixed costs of five thousand six hundred, divided by seven hundred, is eight jobs. Eight jobs is the month where the business breaks even. The ninth job is the first one that makes anything, and it makes seven hundred rather than a hundred, which surprises people who have been thinking in terms of margin percentages.
The mistake in the average
One average job is a useful start and a poor long-term tool, because most businesses run two or three distinct kinds of work with very different contributions.
A service call with almost no materials might contribute nearly all of what it bills. An installation with expensive equipment might contribute a third. If half your months are made of one and half of the other, the single average hides the fact that eight of the wrong kind of job does not break even at all.
Split the work into two or three categories and calculate contribution for each. Most owners find one category they had assumed was carrying the business and one they had assumed was marginal, and the two are frequently the wrong way round.
Where the owner's pay belongs
This is the argument that derails the exercise more than any other. If the owner's own income is treated as whatever is left over, the break-even number is flattering and meaningless.
Put the owner's pay in the fixed pile at the figure it would cost to employ somebody to do that work. The number that comes out is then a real one: the point at which the business covers its costs including the labor of the person running it. Anything above that is a return on the business rather than a wage, and separating the two is what lets you see whether the business is worth owning as opposed to working in.
What happens when you add a second van
Fixed costs do not rise smoothly. They rise in steps, and every step is a decision that changes the break-even count overnight.
A second van with a technician in it adds a wage, a vehicle payment, insurance, tools and phone. That might be several thousand dollars of fixed cost arriving in one month. The break-even count does not go up by one job. It goes up by however many jobs that step costs divided by contribution, which is often four or five, and it goes up on the day the step is taken rather than on the day the new capacity fills.
The gap between those two dates is the risk in every expansion. Knowing the count in advance turns it into a plan with a deadline: the new hire needs to be producing four jobs a month by the end of the second month, and if the pipeline does not contain them, the hire is early.
Margin of safety, and the reason to care
Compare the break-even count against what you actually did last year, month by month. The distance between them is the margin of safety, and it will be uneven.
Most service businesses have two or three months a year where the count is barely cleared, and they are usually the same months every year. Seeing them written down converts a vague sense that February is slow into a planned response: the maintenance contracts sold in the fall, the deferred purchase, the vacation taken then rather than in June.
The costs that hide in the wrong pile
Two classifications go wrong often enough to mention, and both distort the count badly.
Wages for people who are paid whether or not work comes in are fixed, not variable, even though they feel like a cost of the job. A salaried technician on the payroll in a slow February is part of the pile that has to be covered. Only genuinely per-job labor, a subcontractor engaged for one project, belongs on the variable side.
Vehicle costs split across both. The payment, the insurance and the registration are fixed. Fuel and the wear that comes from miles driven are variable. Putting the whole vehicle in one pile or the other makes the contribution figure wrong in a way that quietly moves the break-even count by a job or two.
The version worth keeping
Three lines on one page, updated when something structural changes rather than monthly. Fixed costs per month. Contribution per job, by category. The count.
Once it exists, it answers questions that used to require a feeling. Whether to take a discounted job in a quiet week: yes if it contributes anything and you are past the count, since the fixed costs are already paid. Whether to take the same job in a busy week: probably not, because it displaces a full-price one. Whether you can afford the equipment lease: only if the extra jobs it brings clear the step it adds. Three years of decisions like that add up to more than any single price increase.