Marketing Budget Calculator

How the number is derived

Three approaches are common. A percentage of revenue, which is simple and arbitrary. A goal-based figure, new customers needed × CAC. Or a marginal figure, spending until the last dollar stops returning above threshold.

The third is correct, the second is workable, and the first is what most businesses do.

Budget = target new customers × fully loaded CAC is the practical form for a business that knows both numbers.

An example

A target of 1,000 new customers a month at a $27 CAC requires $27,000. As a percentage of the $58,000 of monthly revenue that is 47%, which sounds alarming.

Checked against the economics: those customers generate $31,900 of first-order contribution and $168,430 over their relationship. The spend is comfortably justified.

A business applying a conventional 10% of revenue rule would budget $5,800, acquire 215 customers, and forgo 785 profitable acquisitions a month.

That is the cost of a percentage rule. It is unconnected to whether the marginal customer is profitable, which is the only question that matters.

The catch

Percentage-of-revenue budgeting is circular: revenue depends on spend, which is set from revenue. It systematically underspends during growth and overspends during decline.

Goal-based budgets assume CAC holds at the new volume, and it does not. Marginal CAC rises as the addressable audience is exhausted, so a plan built on constant CAC overstates what the budget will buy.

What this changes

Set the budget from customer targets and affordable CAC, then adjust against observed marginal returns rather than holding it fixed for the year.

Then check it against the cash the payback period requires. A budget the economics justify and the cash flow cannot fund is not a budget, and that constraint binds long before the efficiency one does.

Why the cash constraint usually sets the budget

For a business with a four-month payback, every dollar of monthly acquisition spend commits roughly four dollars of working capital. A $27,000 monthly budget therefore ties up around $113,000.

That means the budget question for most self-funded businesses is not what is profitable but what is fundable, and the two answers can be far apart.

Businesses that recognise this early tend to work on payback period as a growth lever rather than treating it as a fixed property, because shortening it is what raises the budget the same capital can support. Those that do not tend to hit a ceiling they cannot explain, since every metric says they should be spending more.

Reviewing the budget quarterly rather than annually keeps it connected to what the market is actually charging, since acquisition costs move considerably faster than planning cycles do.

Splitting it into a committed portion and a discretionary one also helps, since the first funds the channels that reliably work and the second funds the experiments that occasionally replace them.

Zero-based budgeting suits this better than incremental budgeting, since last year's allocation reflects last year's channel economics and those move faster than most planning assumptions.

Budgeting as a percentage of revenue is the common approach and it has an awkward property: it cuts spending exactly when revenue falls, which is often when spending matters most. Budgeting from a target cost per acquisition and a growth objective produces a figure driven by what you are trying to achieve rather than by what happened last quarter, and it survives a bad month better.