Free calculator
CAC calculator
Spend divided by customers, like every other one. Then the part the others leave out: take the spend that reached a page which could not convert anybody, lift it out of the numerator, and see the CAC you would have had.
The third slider starts at zero because a calculator that assumes waste in order to make its own point is a sales pitch with sliders on it. Nothing here estimates revenue you would have earned: spend that reached a destination which cannot convert bought nobody by definition, so it lands on the fraction as pure numerator. One thing is assumed, and it is the only neutral option — that the dead spend would have converted at the rate the rest of it did. Assume that and the extra customers and the extra spend cancel exactly, which is why the figure above needs no revenue model. If the broken destination carried your worst traffic, the real number is a little higher than this; if it carried your best, a little lower.
What this counted
The formula, and which convention is in the box
Customer acquisition cost is acquisition spend ÷ new customers, over the same period for both. The slider above takes whatever you put in the first box, so the convention is yours: media only, or media plus the salaries, tools and agency fees that made the campaigns exist. The second is always the larger number and is the one a board means. Whichever you use, publish it beside the figure — most disagreements about CAC turn out to be two people using different definitions.
The longer version — what belongs in the numerator, the trap in the denominator, what a good CAC is, and the reason it moves that nothing in an ad account reports — is on the customer acquisition cost page.
Why this sits on a monitoring site
A broken destination moves CAC the whole way
Most marketing waste is partial — a campaign that converts worse than another, an audience that is slightly too broad. It moves the fraction a little. Spend that reaches a destination which cannot convert anyone is different in kind: it adds to the numerator and contributes exactly nothing to the denominator, so it moves CAC by its full value.
It is also the one kind that shows up in a report as something else. A CAC that rose 30% reads as an auction problem, a creative problem, a seasonality problem — and a page answering 200 OK while telling visitors it does not exist produces the same chart. In INC-2291 that was $12,480 at $58.59 a minute across 3 campaigns, and every dollar of it landed on CAC as pure numerator.
Which is why the honest next step after a calculator is not a subscription. It is checking whether the page is broken right now, which is free and takes about three seconds.
Common questions
Customer acquisition cost, answered plainly
How do you calculate customer acquisition cost?
Divide the total spend on acquiring customers in a period by the number of customers it brought. The argument is usually about what belongs in the numerator — paid media alone, or media plus salaries, tools and agency fees. Either convention works as long as it does not change between periods, because the number is only useful as a trend.
What is a good CAC?
There is no universal figure, because CAC is only meaningful against what a customer is worth. The usual benchmark is lifetime value to CAC of about 3:1, and a payback period under twelve months for most subscription businesses. A CAC that looks high against a competitor’s is not automatically a problem; a CAC that moved 20% in a month without anything changing in the market almost always is.
Why did my CAC suddenly increase?
Before assuming the auction got more expensive, check the denominator and the destination. CAC is spend divided by customers, so it moves just as far when conversions stop as when costs rise — and the cheapest way to stop conversions is a landing page that quietly broke while the campaign kept paying for clicks into it. That failure looks exactly like a rising CAC in a report, and nothing in the ad account reports it.
Does wasted ad spend affect CAC?
Directly and fully. Spend that reaches a destination which cannot convert anyone brings no customers, so it adds to the numerator and nothing to the denominator — it moves CAC by its whole value. That is unusual: most marketing inefficiency is partial, and this kind is total.
Should CAC include salaries and tools?
Fully loaded CAC includes the team, the tools and the agency; paid CAC includes only media. Fully loaded is the honest number for a board, paid CAC is the actionable one for a channel decision. Publish which one you are using next to the figure, because most disagreements about CAC turn out to be two people using different definitions.
The third slider starts at zero, and that is the whole design of this page. It would convert better set to something — a default of a few per cent would make the saving appear before the reader had agreed to it. But the number belongs to them, and a calculator that supplies its own premise is not a calculator. If they set it to zero and leave with a plain CAC figure, the page has still done its job, which is to be the one they trust the next time the number moves.