How to Calculate Your True Cost Per Job (And Why Most Owners Get It Wrong)

Ask most trade or service business owners how much a job costs them, and they'll give you a number. Materials plus labour. Maybe a fuel allowance. That's the sum, and the sum is wrong — not by a small margin, but often by 20–35% of the true figure.

This matters for one reason above all others: if you don't know your true cost, you cannot know your true margin. You might think you're making 40% gross profit on a job when you're actually making 25%. You might think your smallest jobs are worth taking. They might not be. You might have one type of work that subsidises another without ever realising it.

The fix is not complicated. It requires including all the costs that belong to a job — not just the obvious ones. Here's how to do it properly.

The Visible Costs

These are the costs every owner already counts:

• Materials and parts — everything consumed or installed during the job
• Direct labour — the hours paid to the person doing the work, at their hourly cost to you (salary plus employer NI plus pension contribution)
• Subcontractor costs — if you bring in external resource for specific jobs

These costs are real and most businesses track them reasonably well. The problem is that they represent only part of the picture. Everything below is also a real cost of that job — it's just less visible.

The Hidden Costs

These are the costs that are genuinely attributable to the job but rarely appear in a per-job calculation:

Vehicle depreciation and running costs. If a van is used to travel to and from jobs, that van costs money every mile. Depreciation, insurance, servicing, tyres, fuel — divided across the number of jobs the van serves per year, this is a real cost per job. For a business running one van doing 200 jobs per year, total van costs might be £8,000–£12,000 annually — that's £40–£60 per job before a single bolt has been turned.

Tool and equipment wear. Power tools, specialist equipment, consumables — these are not free. They depreciate with use. A business that spends £3,000 a year on tool replacement across 300 jobs is spending £10 per job on tools, whether it counts it or not.

Admin time per job. Someone has to quote the job, schedule it, raise the invoice, chase payment if it's late, and file the paperwork. For a straightforward job, this might be 30 minutes of office time. At £15–£20 per hour fully-loaded, that's £7.50–£10 per job in admin cost alone. For complex jobs requiring site visits to quote, the admin burden can reach 2–3 hours.

Travel time. If your operative spends 45 minutes travelling to a 2-hour job, you have paid for 2 hours 45 minutes of time to deliver 2 hours of chargeable work. That 45-minute travel overhead is a real cost. At £18/hour fully-loaded labour cost, that's £13.50 per job that never appears in a simple materials-plus-labour calculation.

Warranty callbacks and rework. Every business has a recall or rework rate — jobs that require a return visit because something wasn't right. If your callback rate is 5% and a callback costs 2 hours plus travel, you should add 5% of that cost to every job. A business ignoring this is effectively averaging its rework cost across all jobs without knowing it.

Rebooking and cancellation cost. When a customer cancels at short notice, there is often a real cost — a slot that couldn't be refilled, labour paid for work not done. Across a year, this can be significant. If you lose two productive hours per week to late cancellations, that's 100 hours of paid labour per year with no corresponding revenue — approximately £1,800–£2,500 absorbed silently by your job cost base.

How to Build a True Cost Per Job Formula

Here is a worked example for a sole-trader heating engineer running one van, doing approximately 300 jobs per year (a mix of service calls and small installations).

Cost Element	Annual Cost	Per Job (÷300)
Materials (average per job)	—	£45
Direct labour (4hrs @ £20/hr fully-loaded)	—	£80
Vehicle — fuel, insurance, servicing, depreciation	£9,600	£32
Tools and equipment replacement	£2,400	£8
Admin time (45 mins per job @ £18/hr)	—	£13.50
Travel time (40 mins avg per job @ £20/hr)	—	£13.33
Rework/callback allowance (4% rate, 2hr callback)	—	£6.40
Overhead allocation (rent, phone, software, insurance — £18,000/yr)	£18,000	£60
True cost per job		£258.23

The simplified calculation — materials plus direct labour — would give £125. The true cost is over twice that. A job quoted at £300 looks like £175 gross profit on the simplified model. It is actually £42 — a 14% gross margin, not 58%.

What Your True Cost Per Job Tells You About Your Pricing

Once you know your true cost per job, pricing becomes a different conversation.

First, you establish your floor. The true cost is the minimum you can accept for any job and still cover all costs. Any quote below that number loses money in real terms, even if it looks profitable on a simple model.

Second, you can set a target margin. If your business requires a 30% net margin to meet its obligations and pay you a fair wage, you add 30% to the true cost floor and that is your minimum quote. No guesswork. No gut feel. A number with a clear rationale behind it.

Third, you can identify which jobs or job types are genuinely profitable. Some jobs look average on revenue but are cheap to deliver — short travel, standard materials, no rework. Others look high-value but carry high hidden costs. Knowing which is which is the difference between filling your schedule with profitable work and filling it with busy work.

Using Cost Per Job to Find Your Most and Least Profitable Work

Most SMEs have never done a proper profitability analysis by job type. When we run this analysis as part of a Diagnostic Assessment, the results are consistently surprising.

The pattern is usually the same: 20–30% of a business's job types generate 60–80% of its real profit. Another 20–30% are borderline — they cover costs but contribute little to net profit. And 10–20% are genuinely unprofitable when all hidden costs are included.

To find your own distribution, do this:

1. List your five to ten most common job or service types.
2. Build a true cost model for each one — same methodology as above, but with the specific cost profile of that job type (travel distance, materials, labour intensity, rework rate).
3. Compare the true cost against the average revenue you receive for each type.
4. Rank them by real gross margin percentage.

What you typically find: your smallest, most frequent jobs have the worst real margin because the fixed overhead per job (admin, travel, vehicle) is spread across a small revenue base. Your larger, less frequent jobs often carry the best real margin even though they feel harder to win.

What to Do With This Information

The true cost per job analysis feeds directly into Pillar 1 (Financial Health) and Pillar 4 (Operations and Scheduling) of our Diagnostic Assessment. It tells you not just what you are earning, but where you are earning it — and where you are spending resources that aren't generating a return.

Practically, the actions that follow are:

• Raise prices on your least profitable job types, or stop taking them
• Prioritise marketing and sales effort toward your most profitable job types
• Reduce hidden costs — batch admin, reduce travel time through better scheduling, cut callback rate through better quality control
• Build the true cost model into your quoting system so every quote reflects reality, not a simplified approximation