Your report every week gives you the same metrics: spend, clicks and conversions.
While the figures are always accurate, they don’t actually provide you all the information you need to monitor how your campaign is performing. Because the question that needs to be answered isn’t how much you spent on your campaign. The important questions are, which campaign is draining the budget? And which ones are carrying the account?
Wondering how to answer these questions? Here’s a single ratio to pay attention to.
Why You Shouldn’t Rely on Raw Metrics
Which campaign produces the most conversions in your account? Think about it. Now you would think that the next best thing is to keep it. But that’s where you would be wrong.
Just because a campaign brings in sales doesn’t mean it’s paying off. If it consumes 60% of your budget and delivers only 40% of your conversions, it’s pulling your blended performance down.
Raw conversion counts rewards the campaigns with the biggest budgets. This is why you can’t fully rely on them and that’s the bias you want to strip out before you decide where money goes next month.
So how can this be fixed?
The Efficiency Index
The solution isn’t to pull down all your campaigns and start again because of the existing bias. You need to weigh two factors:
- How many conversions a campaign earns
- How much of spend it consumes
Efficiency Index = share of total conversions ÷ share of total spend
Share of conversions is the total number of conversions a campaign made across all your active ones. Share of spend, on the other hand, is its spend divided by the total spend across your accounts. Divide one by the other, and you get a clean, unitless number you can rank.
Read it like this:
- A score of 1.0 means the campaign returns conversions in exact proportion to the budget it uses. That is your baseline.
- Below 1.0 means it is underperforming. It takes more budget share than it gives back, and lower is worse.
- Zero means it is spending and converting nothing. Flag it immediately.
- Above 1.0 means it is overdelivering, earning more than its fair share of the budget. See Pareto rule, aka the 80/20 rule. 80% of your results will always come from 20% of your efforts.
Since both shares total 100 percent across the pool, the weighted average of every score is always a clean “1”. “Below 1” means “below your own portfolio average,” with no arbitrary target to mule over during your next client call.
Why Share of Conversions Beats Average Conversions per Week
Average conversions may seem like the best way to analyze campaigns. However, an average is an absolute count, and you cannot weigh an absolute count against a spend baseline without dividing by spend, at which point you have just rebuilt the cost per conversion metric.
Share of conversions is already a normalized metric, so it sits opposite spend share naturally inside one ratio. This method is also a great way to track the performance of trends. All you have to do is use the weekly (or any time frame) average to track a single campaign against its own history.
How To Implement the Efficiency Index
Download your campaign data, then sort ascending conversions. The lowest scores are your budget drains with the highest spend. But before you cut campaigns based on this spend-to-conversion ratio, consider a couple of things.
Firstly, low volume makes the number a little untrustworthy. In scenarios in which you have only ten or fewer total conversions, a single conversion swings heavily. Follow the Central Limit Theorem, which suggests that a sample size of 30 often makes a sampling distribution close to normal. This simply means that a low conversion or spend level lessens the accuracy of any measurement.
This is why platforms such as Meta Ads have an extended learning phase. The system is striving to reach statistical significance so that its analysis is trustworthy. When pulling reports, it may help to widen your date window to get a statistically significant number of conversions or spend.
Secondly, the Efficiency index is relative, not absolute. It ranks your campaigns against each other, but every campaign in the pool could be unprofitable, and the calculation would still find a winner. You don’t want to have a “the best out of the worst” scenario.
Taking these two factors into consideration stops you from killing a campaign that may score low on the curve but still hits the number you really care about.
Tips for Setup
For keywords, calculate the shares within the ad group or campaign rather than the whole account. If not, a cheap keyword sitting inside an expensive campaign will look better than it deserves.
If your conversions carry different values (a quote request versus a signed contract), swap conversion count for conversion value within the share calculation. The ratio behaves the same way and now reflects revenue rather than raw events.
Conclusion
It’s easy to get overwhelmed when there are a lot of metrics to pay attention to as a paid media manager. But if you’re able to focus on the efficiency index, you’ll be able to focus on what truly matters.
There’s no point in running a hundred campaigns and getting conversions if you’re spending more than you’re getting back.
Ready to change that? Start with this simple ratio.
Knowing how the Google Ads auction works is one thing. Spotting where your own account is wasting money is another.
That’s why I put together this Free Google Ads Audit Checklist. It’s the same process I use to review six-figure accounts: 15 checks, ranked by priority and graded so you can quickly see what needs attention.
The first check compares two numbers from different reports. On one national retail account, it uncovered 96,000 clicks that had been paid for but never delivered a sale. That’s A LOT of waste. The same thing could be happening in your account.
Open your account in another tab and give it an hour. You might be surprised by what you find.
