Picture the whiteboard in the corner of a small contractor's office, the one with the week's jobs written on it in marker and rubbed out every Friday. It shows what is happening and nothing about whether it is enough. Somewhere beneath that list is a number, specific to this business and this year, below which the month loses money no matter how hard anybody worked or how well the jobs went. Most owners have never worked theirs out, largely because it sounds like accounting and is actually arithmetic that fits on one sheet of paper.
Separating the Costs That Do Not Care How Busy You Are
The whole calculation rests on splitting the outgoings into two piles, and the split is easier than it looks because most items are obviously one or the other. Rent on a yard or a unit, insurance premiums, vehicle payments and their insurance, phone and software subscriptions, accounting fees, licenses and any wage that gets paid whether or not there is work all belong in the fixed pile. They arrive at the same size in a quiet month as in a busy one, which is precisely what makes them dangerous.
The variable pile is everything consumed by doing a job: materials, disposal, subcontracted labor, fuel attributable to the work, equipment hire, and any pay tied to hours actually worked. The awkward cases sit in between and can be assigned by judgment rather than by principle, since a small error here moves the final answer very little. What matters is that the fixed pile is complete, because anything left out of it makes the break even number look better than it is.
What Each Job Actually Leaves Behind
Take a typical job, or better, take last year's invoices and pick the middle of the range rather than the biggest one anybody remembers. Subtract from its price everything in the variable pile that job consumed. What is left is the contribution: the money that job contributes toward the fixed costs and, eventually, toward profit. This is not the same as profit on the job and it is not the same as markup, and confusing either with contribution is the single most common error in this exercise.
Businesses that do several distinct kinds of work should run this separately for each, because the contributions frequently differ far more than the prices suggest. A service call with almost no materials can contribute more than a large installation whose price is mostly parts passing through the business at a modest margin. Owners who discover that pattern often find that the job type they were quietly hoping to grow is the one carrying the least of the load.
Dividing One Number by the Other
Add the fixed pile for a month, divide it by the contribution from a typical job, and round up. That is the number of jobs at which the month breaks even, and every job above it contributes almost entirely to profit because the fixed costs have already been covered. The figure is usually higher than the owner expected, and the reaction to seeing it for the first time is frequently a quiet reassessment of a couple of months that had felt fine.
The version that includes the owner's own pay is the one worth using in practice. A break even that leaves nothing for the household is a break even for the business and a loss for the person running it, so add the required draw to the fixed pile and calculate a second number. The distance between those two figures is the clearest picture most small owners will ever get of how much of the month is spent working for the business rather than for themselves.
What the Number Is Good For
Its first use is pricing. A job offered below the point where it makes a normal contribution can still be worth taking in a month already past break even and is close to indefensible in a month that is not, and knowing which situation you are in converts a gut feeling into a decision. Its second use is capacity: if the break even number is uncomfortably close to the maximum number of jobs the business can physically deliver, the problem is structural rather than commercial and no amount of selling will fix it.
Its third use is testing anything that changes the fixed pile. A second van, a first employee, a bigger unit or a piece of equipment all raise the fixed costs by a knowable amount, and dividing that amount by the contribution per job gives the number of extra jobs the decision requires every month, forever. That framing turns a large and emotional purchase into a straightforward question about whether the extra work exists. The Small Business Administration's counseling programs walk owners through exactly this kind of arithmetic at no charge, and the exercise is far more useful done once with somebody than read about repeatedly.
Keeping It on the Wall Rather Than in a Drawer
Redo the calculation whenever the fixed pile changes materially and at least once a year, since insurance, rent and vehicle costs drift upward without any single increase being large enough to notice. Write the current figure somewhere visible, because a number that lives in a spreadsheet nobody opens has the same practical effect as never having calculated it. Two numbers on a wall, the break even and the one that includes a proper wage, are enough.
Which puts something useful next to that whiteboard of the week's jobs. The list has always shown how busy the business is. What it never showed was whether busy was sufficient, and that question has a specific answer that does not change from week to week and does not depend on anybody's mood on a Friday afternoon. An hour of arithmetic produces it, and having produced it once, most owners find they can no longer look at a month's schedule the same way.