23 September 2026 · 5 min read · Oscar Markham
If you only measure one thing, measure this
Marketing reports are full of numbers that feel informative and change nothing: impressions, reach, followers, clicks, time on page. If you only had one figure to run your business on, none of those would be it.
The number
Cost per job won. Not cost per click, not cost per lead, not cost per enquiry. What it cost you in advertising to end up with one customer who paid you.
Everything upstream of that is a diagnostic. Only this one connects to whether you should spend more money or less.
How to work it out
Total advertising spend for the month, divided by the number of jobs that came from advertising. The second number requires you to ask every customer where they came from, and to write it down.
That is the hard part, and it is the reason most businesses do not have this figure. It is also an hour a month of work at most.
- Total ad spend for the month
- Number of jobs won that came from advertising
- Divide one by the other
- Compare against the contribution margin of an average job
- If it is well below, spend more. If it is close, fix conversion before spending more
What it tells you that the other numbers do not
A campaign with a rising cost per lead may be perfectly healthy if those leads convert far better. A campaign with a falling cost per lead may be quietly destroying your margin by attracting price shoppers.
Only the cost per job won shows you which is happening, and it frequently contradicts what the platform dashboards appear to say.
The numbers worth keeping as diagnostics
Cost per lead, to spot when something breaks. Lead-to-job conversion, because it tells you whether the problem is marketing or sales. Response time, because it explains most conversion problems.
Those three explain why the main number moved. They are not the main number.
What to ignore entirely
Followers, impressions, reach, engagement rate, time on site, bounce rate. None of them pay anybody's wages and all of them can be improved while the business gets worse.
If a report you receive leads with those, ask what the cost per job won was. The answer, and the reaction, will tell you a good deal.
Written by Oscar Markham, founder of Dublin Growth Digital. We run lead generation for Irish estate agents and trades, reported every Friday in enquiries and booked work.