The Hidden P&L Impact of Google's Smart Bidding Defaults
Google's default bidding settings are designed for one thing: spend efficiency from Google's perspective. Not yours.
When you set up a new campaign or inherit an existing account, the bidding strategy defaults are already configured. Most brands assume these defaults are neutral. They're not.
Smart Bidding defaults are optimised to maximise conversions or conversion value at the lowest perceived risk to Google's algorithm. That's not the same as maximising your profit.
The algorithm doesn't know your margins. It doesn't know your cash flow cycle. It doesn't know which products fund your business and which ones drain it.
What the Defaults Actually Do
Maximise Conversions
Finds the cheapest conversions first. Often branded search, remarketing, and low-intent traffic that would have converted anyway. You pay for demand you already owned.
Target ROAS (Blended)
Optimises to a single revenue target across all products. A 60% margin SKU and a 15% margin SKU get treated identically. One funds profit, the other erodes it.
Conversion Value Maximisation
Chases revenue, not profit. High-AOV, low-margin products get prioritised because they look good in-platform. Your P&L tells a different story.
The P&L Translation Problem
Here's what happens when you run Smart Bidding without commercial context:
Looks acceptable. But when you break it down by product:
The algorithm pushed 70% of spend toward products that lost money. The blended ROAS hid it.
Why This Happens
Smart Bidding is designed to hit targets. If your target is a blended 4x ROAS, the algorithm will find the path of least resistance. That path is usually:
- Branded search (high conversion rate, low intent quality)
- Remarketing to existing customers (easy wins, cannibalised organic)
- High-AOV products (revenue looks good, margin ignored)
- Sale items and clearance (conversion rate spikes, profit collapses)
None of this is malicious. It's just how the algorithm works when it doesn't have commercial context.
How to Reconfigure for Commercial Outcomes
Segment by margin, not just category
Create campaign structures that group products by margin tier. High-margin SKUs get different ROAS targets than low-margin SKUs.
Use value rules to inject margin data
Google's conversion value rules let you adjust reported value based on audience, device, or location. Use them to weight high-margin products higher.
Set break-even floors, not just targets
Know your break-even ROAS by product group. Set minimum ROAS thresholds to prevent the algorithm from chasing volume into loss-making territory.
Separate brand from non-brand
Never let Smart Bidding blend branded and non-brand performance. The economics are completely different. Treat them as separate P&L lines.
The goal isn't to abandon Smart Bidding. It's to give the algorithm commercial constraints so it optimises for your business, not just its own efficiency metrics.
The Audit Question
When was the last time someone mapped your bidding strategy against your margin structure? If the answer is "never" or "I'm not sure", your P&L is being shaped by defaults that don't know your business.
Related Reading
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