Budget Allocation Across Meta, Google, and TikTok

Chapter 1The Static Budget Trap

Most brands set their channel budget at the beginning of the quarter and don't touch it until the next planning cycle. “60% Meta, 30% Google, 10% TikTok” gets written on a slide deck and becomes gospel for three months. This is exactly wrong.

The optimal allocation between channels changes weekly, sometimes daily. Creative fatigue on Meta can shift your best marginal dollar to Google. A competitor pulling TikTok spend can open up cheap inventory. Seasonal demand patterns hit different channels at different times. A static budget ignores all of this, leaving meaningful efficiency on the table.

Chapter 2Understanding Diminishing Returns

Every advertising channel follows an S-curve of diminishing returns. The first chunk of spend on Meta can generate strong ROAS. The next chunk generates less. The chunk after that less still. At some point, the marginal dollar on Meta generates less return than the marginal dollar on Google, and that's where you should shift spend.

The problem is that the point of diminishing returns is different for every channel, changes over time, and isn't visible in platform dashboards. Platforms show you average ROAS, not marginal ROAS. Average ROAS can look great even when your marginal dollar is generating negative returns, because past efficient spend masks current inefficiency.

Chapter 3The Allocation Framework

Here's the framework Sam uses to determine optimal allocation. It runs continuously, but you can apply the same logic manually on a weekly basis:

1. 1

   Start with corrected data

   Use Parker's correction factors, not platform-reported ROAS. If you're allocating based on inflated numbers, you're optimizing for the wrong thing.

2. 2

   Calculate marginal ROAS per channel

   Look at the incremental ROAS of your most recent spend increase (or decrease) on each channel. This tells you the actual return of your marginal dollar.

3. 3

   Equalize marginal returns

   The optimal allocation is where the marginal iROAS is equal across all channels. If Meta's marginal iROAS is 2.8x and Google's is 1.9x, shift money from Google to Meta until they equalize.

4. 4

   Apply constraints

   Account for minimum viable spend (you need enough on each channel to clear the learning phase), creative availability, and strategic considerations (brand presence, new channel testing).

5. 5

   Monitor and rebalance weekly

   Creative fatigue, competitive shifts, and seasonal changes mean the optimal point shifts constantly. Check marginal returns weekly and rebalance when the gap between channels exceeds 15%.

Chapter 4Cross-Channel Effects

Channels don't operate in isolation. When you increase Meta prospecting spend, branded search volume on Google goes up. When you pause TikTok, you lose the awareness effect that was feeding your retargeting funnel. These cross-channel effects are invisible in single-channel analysis but critically important for allocation.

Chapter 5Sam in Action

Everything in this guide is what Sam runs continuously. Sam ingests corrected attribution data from Parker, forecasts from Felix, and your business constraints to simulate thousands of allocation scenarios and recommend the optimal budget split.