CAC calculator

By Mathéo Ballasse · June 18, 2026

The formula

CAC = (marketing spend + sales spend) divided by the number of new customers over the same period. For an honest CAC, include salaries and tools, not just advertising.

A concrete example

Picture $8,000 of marketing and sales spend over a month, salaries and tools included, for 20 new customers signed. Your CAC is $400 per customer. That number means nothing on its own: it takes on meaning against what a customer brings you over their entire lifetime.

How to read your CAC

A CAC is neither good nor bad in absolute terms. Three reference points make it readable: the LTV-to-CAC ratio (aim for at least 3, otherwise you pay too much for your customers relative to what they return), payback time (ideally under 12 months), and its trend over time (a CAC that climbs channel by channel signals the lever is saturating).

The traps that skew the number

• Amputated CAC. Keeping only the ad budget and forgetting salaries, freelancers and tools. The real cost is always higher than you hope.
• Wrong customer scope. Counting free signups or plain leads as customers inflates the denominator and artificially crushes the CAC.
• Timing mismatch. Matching one month of spend to customers signed the same month when your sales cycle runs several weeks.
• Misleading blended CAC. A single global number can hide a channel burning cash behind a flattering average.

How to lower your CAC

• Improve your conversion rate at each step of the funnel: the same budget then signs more customers.
• Rebalance your budget toward your cheapest channels by real CPA, not by the advertised cost per lead.
• Activate low marginal-cost levers like content, SEO or customer referral.
• Shorten your sales cycle: less sales time per customer means less cost per customer.

CAC is never judged alone

Is a CAC of $400 good? Impossible to answer without comparing it to what a customer brings you. The most widely used benchmark comes from David Skok, the investor who formalized SaaS metrics in his SaaS Metrics framework: aim for a lifetime value (LTV) at least three times your CAC. Below that, you pay too much for customers relative to what they return. Skok is clear that this ratio of 3 is a viability floor, not a trophy: clearing it means your model holds, not that you have won.

Take the example of a $400 CAC for a $40-per-month subscription. If your customers stay two years on average, each brings $960 before margin, a ratio of 2.4. That is below the floor: you must either lower your CAC, keep customers longer, or raise your price. The same CAC becomes very good if your customers stay four years. A CAC only makes sense against lifetime and margin, never on its own.

Why your CAC looks catastrophic at the start

At the 0-to-1 stage, your CAC is almost always terrible, and that is normal. You sell by hand, one at a time, spending hours on video calls to sign a customer at $30 a month. Run through the math and you get a cost per customer that seems absurd. Do not draw conclusions too early: at this stage, the number does not measure the profitability of your acquisition, it mostly measures that you are doing things that do not scale in order to learn. That is a good thing, not a problem.

CAC becomes a real steering metric the day you start repeating a channel. Then its value, and above all its trend, tell you whether the lever scales or saturates. While you are still hunting for your first channel, watch the signal (do people pay, come back, refer you) more than the cost. You optimize cost once you have proven the channel works, not before.

A number you track over time

A CAC is not meant to be computed once and filed away. What matters as much as its value is its trajectory. A CAC that stays stable while you grow is a very good sign: your acquisition scales. A CAC that climbs month after month on the same channel signals the opposite, that you are starting to scrape the bottom of the pool, that auction competition is rising, or that you are widening your targeting toward colder prospects.

The right reflex is to track your CAC channel by channel, over periods long enough to smooth out spikes, and set it next to your payback and your customer lifetime. It is that trio, not CAC in isolation, that tells you whether you can accelerate safely or whether you first need to fix your model. A dead-simple table, updated each month, beats the perfect number computed once.

The right time to use it

One last point of method: the ratio between lifetime value and CAC is only truly reliable once you have enough customer history to estimate a credible lifetime. Very early on, you know neither your real churn nor how long customers stay, so any LTV is a guess. Computing a precise ratio on invented data gives false confidence, which is worse than no number at all.

The right use at this stage: measure your raw CAC and your payback, simpler and more honest, and save the LTV-to-CAC ratio for when you have several months of retention behind you. An approximate but real number always beats a brilliant ratio built on assumptions. CAC is a decision tool, not a beauty contest: use it to make calls, not to reassure yourself.

Frequently asked questions

What is a good CAC for a SaaS?

There is no universal threshold: a good CAC is judged against lifetime value (LTV) and payback time. Aim for an LTV-to-CAC ratio of at least 3.

Should salaries be included in CAC?

Yes. A complete CAC includes marketing AND sales costs, salaries and tools included, not just the ad budget.

Over what period should you calculate CAC?

Take a period long enough to smooth out spikes, a quarter is a good compromise, and match the spend to the customers won over that same period. Account for lag: money spent this month may sign a customer next month.

Blended CAC or per-channel CAC?

Blended CAC mixes all your channels into one number: handy for an overview, but it hides the gaps. To allocate budget, compute CAC channel by channel, that is where the profitable levers and the money pits hide.