Building an annual marketing budget forecast bottom-up

A common shortcut for annual marketing budgeting is setting spend as a fixed percentage of projected revenue. It's easy to calculate and easy to defend to a board, but it doesn't tell you whether that amount of spend, allocated to your actual current channel mix, will realistically produce the growth target attached to it.

A bottom-up forecast instead starts from each channel's current cost per result and expected efficiency at different spend levels, sums the resulting pipeline or revenue contribution, and checks that total against the growth target before the budget is finalised.

Where the bottom-up total falls short of the top-down target, that gap is worth surfacing explicitly — either the target needs to adjust, new channels need testing budget, or current channels need efficiency work before more spend will help. Presenting that gap honestly tends to land better with a board than a forecast quietly built to match the target regardless of the underlying numbers.