Why is my cost per lead higher than last year?

Cost per lead is a ratio, not a price

Start with how it is actually computed, because the definition does the work.

Google defines the metric plainly: "Average cost per action (CPA) is calculated by dividing the total cost of conversions by the total number of conversions."

Now put the denominator in terms of clicks. Microsoft states the conversion rate formula directly: "The formula for calculating the conversion rate is (Conversions / Clicks) x 100."

Rearrange those two and the shape appears. Your conversions are your clicks multiplied by your conversion rate. Your cost is your clicks multiplied by what each click costs. The clicks cancel, and what is left is simple: cost per lead is the price of a click divided by the share of clicks that turn into leads.

That is arithmetic from the two definitions rather than a claim either company makes in those words, so treat it as a way of reading the number rather than a quotation. It holds well enough to reason with, and it changes what you look at.

So there are exactly two levers. What you pay to get someone to the site, and how well the site turns them into enquiries. Everything else acts through one of those two.

A ratio moves more than either of its parts

Here is the part that surprises people, and it is worth doing on paper once.

Say a click cost 4 dollars last year and 4 dollars 40 now. That is a 10 percent rise, which nobody would panic about. Say the conversion rate was 5 percent last year and is 4.5 percent now. That is a 10 percent fall, which nobody would notice.

Last year: 4 dollars divided by 5 percent, so 80 dollars a lead. This year: 4 dollars 40 divided by 4.5 percent, so about 97 dollars 80. That is a rise of roughly 22 percent.

Two changes nobody would report separately produce a change everybody notices. They do not add to 20 percent. They compound, because one is in the numerator and one is in the denominator.

The same arithmetic runs the other way, which is the useful half. Recovering 10 percent on the conversion rate is worth slightly more than shaving 10 percent off the click price, and it is usually the cheaper of the two to attempt. The lever nobody is bidding against you for is the one on your own website.

The denominator may not be leads

Before accepting the number, check what is being counted, because the word lead is doing a lot of unexamined work.

Google is explicit that a conversion rate can exceed 100 percent: "If you're tracking more than one conversion action, or you choose to count 'Every' conversion, your conversion rate might be over 100% because more than one conversion can be counted for each interaction."

Read the consequence backwards. If more than one conversion can come from a single interaction, then the denominator of your cost per lead is not necessarily a count of people. It is a count of recorded actions, and one person can produce several.

That has a specific effect on a year over year comparison. If somebody added a second conversion action at some point, a form and a phone call for instance, the count went up without the business changing. Cost per lead would have dropped for reasons that have nothing to do with performance, and it would climb back the moment that action is removed or fixed.

So the honest first question is not why the number moved. It is whether the same thing is being counted in both periods.

Your target may have followed the problem

This one explains why nothing flagged the drift while it was happening.

If the campaign uses Target CPA bidding, Google says where its suggested number comes from: "The recommended Target CPA is the average CPA from the last 30 days, adjusted for any conversion delays".

Sit with that. The recommended target is a reflection of your own recent results. Accept it repeatedly and the target walks upward alongside the thing you wanted it to catch. It never objects, because it was derived from what already happened.

Google is also candid that hitting a target is not guaranteed, and names the reasons: "your actual CPA depends on factors outside Google's control, like changes to your website or ads or increased competition in ad auctions. Additionally, your actual conversion rate can be lower or higher than the predicted conversion rate."

Both of the levers from earlier are in that sentence. Competition moves the price. Your website moves the rate. Google is telling you which parts it does not control, and those are exactly the parts you do.

There is a trap in the obvious response, and Google names it. The instinct on seeing a high cost per lead is to lower the target, which does tend to lower the number. It also does something else: "Setting a target that's too low, for example, may cause you to forgo clicks that could result in conversions, resulting in fewer total conversions."

So you can improve the ratio and end up with fewer leads. That is worth saying plainly, because cost per lead is a measure of efficiency and a business runs on volume as well. A cheaper lead you did not get is not a saving.

What to check, in order

Five checks, and the first four are free.

• Pull the click price and the conversion rate for both periods separately, before looking at cost per lead at all. The combined number cannot tell you which input moved.
• Confirm the conversion actions are identical in both periods. A conversion action added or removed changes the denominator without changing the business.
• Work out which input contributed more. Divide this year's click price by last year's, do the same for conversion rate, and the larger deviation is where the work is.
• If a target bid strategy is running, find out when the target last changed and who or what changed it. A target that tracked your results upward explains a quiet drift.
• Only then consider the auction. It is the input you influence least and the one most often blamed first.

One caution on the arithmetic above. It assumes clicks and conversions are being counted over the same window, and conversions can be credited to a date earlier than the day they arrive, which makes a recent month look worse than it will eventually read. Compare settled periods rather than the last few weeks, and compare months of similar length.

The figures here are an illustration. The method is the point: cost per lead is a compound number, and the first useful act is to take it apart. Working out which half of that ratio is actually moving, and whether the same thing is being counted on both sides of the comparison, is part of what we do on paid search.

Terms used on this page

• Cost per acquisition
• Conversion rate
• Cost per click

Sources

• Average CPA: Definition (Google Ads Help)
• Conversion rate: Definition (Google Ads Help)
• About Target CPA bidding (Google Ads Help)
• Report attributes and performance statistics (Microsoft Advertising, Microsoft Learn)

Last reviewed 2026-09-11.