CAC calculator

CAC is total sales and marketing cost divided by new customers won. Nine thousand of media plus a thousand of salaries across 100 customers is a fully loaded CAC of 100 — against a media-only figure of 90.

The period mismatch is the subtle error. Spend in January often wins customers in March, so dividing one month spend by the same month customers is noisy at best and wrong at worst for anything with a long consideration cycle. Using a rolling three-month window smooths it. The other judgement is which customers count: including those who arrived organically makes CAC look better but makes it useless for deciding how much more to spend, since organic arrivals do not scale with budget.