Parts Gross Profit vs Labour: The Number Most Garages Cannot See

Ask a workshop owner how last month went and you will get a labour answer.

Hours sold, hours attended, efficiency, maybe recovery rate against the door rate. They will know it to a decimal place, and they will know whether it was better or worse than the month before. It is the number the business is run on, and for good reason.

Then ask what parts made and watch the answer change shape. "Parts are decent." "We work on about a third." "It's built into the price." These are not numbers. They are impressions, held confidently, by people who are extremely precise about the other half of the same invoice.

That gap is not a failure of attention. It is structural, and it is worth understanding before you try to close it.

Why labour gets measured and parts does not

Labour is measured because something forces it to be.

A technician clocks onto a job. The hours exist as a record whether anyone wants them to or not, and they are attached to the job from the start. The cost of those hours is your wage bill, which you know. Revenue and cost are both captured, both attached to the same job, and the sum falls out of the system whether you ask for it or not.

Parts have no equivalent forcing mechanism. The revenue is captured, because you have to charge the customer and the price goes on the invoice. The cost is captured too, eventually, because the factor sends an invoice and your bookkeeper enters it.

But they are captured in different places, at different times, by different people, and nothing joins them. Parts revenue lives on the job. Parts cost lives in the purchase ledger. The margin is the difference between two numbers that never appear on the same screen.

So it does not get measured. Not because nobody cares, but because measuring it means somebody doing a reconciliation by hand, and nobody is going to do that every month for a hundred jobs.

What "we work on about a third" hides

The thirty-odd percent figure is usually roughly right on average, which is exactly what makes it dangerous. Averages hide the distribution, and it is the distribution that costs money.

Jobs priced from memory. Somebody quoted from what the part cost last time, eight months and two price rises ago. The margin on that line is not a third, it is closer to nothing, and it looks identical to a healthy job on the invoice.

The supplier you always ring first. Not more expensive across the board, which you would have spotted. More expensive on one category, where habit sends you before price does.

The jobs where a part came back. A wrong part, a returned part, a part fitted and then replaced under your own comeback. Every one of those has a cost with no revenue against it, and in an unmeasured system it vanishes into the general sense that parts are decent. The same goes for the surcharge on an exchange unit you never claimed back, which is a leak worth counting on its own.

Internal work. Parts fitted to your own stock vehicles during prep, charged nowhere, costing something. If that never lands on the vehicle, it does not just distort parts, it flatters the retail margin on the car as well. That argument gets its own post: reconditioning is not free just because you did it yourself.

None of these show up in an average. All of them show up in a per-job margin.

Two numbers, not one

The fix is not complicated. It is to stop reporting the workshop as a single lump and start reporting labour and parts as separate lines with their own cost, their own gross profit and their own margin percentage.

The reason to separate them is that they move for different reasons and you fix them in different ways.

A soft labour month is a capacity or a recovery problem. You look at ramps, at technicians, at how much time was written off, at whether the door rate is holding.

A soft parts month is a buying or a pricing problem. You look at who you bought from and what you charged. Those are completely different conversations with completely different actions, and averaging them together guarantees you have neither.

Once the two are separated, the useful questions become askable. Did parts margin move this month, and against what? Which supplier are we spending most with, and is that deliberate? Are the jobs with the worst parts margin a pattern or an accident?

What it takes to get the number

Less than most owners assume, and this is the part worth hearing if you buy everything per job and hold no stock.

You do not need a catalogue. You do not need stock levels, bin locations or a stock take. What you need is for the cost to be recorded on the parts line at the moment the advisor types it, alongside the supplier it came from.

BP-1147 front brake pads. Cost £41.20. Sold £89.00. GP £47.80, 53.7%.

That single change is what makes every report downstream possible, because it is the first time in the process that what you paid and what you charged have been in the same place. We laid out the minimum version in you do not need a stores man to know what parts make you.

One definition to keep straight, because an accountant will ask and you want the right answer ready. Parts gross profit here is revenue minus the cost recorded on the line. It does not include carriage, it does not include labour, and it carries no share of overhead. It is the margin on the part, not the profit of the business.

What changes when you can see it

The honest version is that nothing changes in the first month. You get a number, and mostly you find out whether your instinct was right.

It is the second and third months that pay, because you now have a comparison. A parts margin that drifts down over a quarter is a pricing problem that used to be invisible until it was a year old. A supplier whose spend climbs while margin falls is a conversation you can now have with evidence rather than a feeling.

That is the real argument for measuring parts. Not that the number is interesting on its own, but that a number you can compare is a number you can manage, and an impression is not.