Smart Bidding is the system through which Google Ads automatically adjusts bids by predicting conversion probability at every auction moment. Signals like device, location, time of day, and remarketing list are all evaluated simultaneously — at a speed and complexity no manual bidding approach could keep up with.
The system isn’t a single strategy but four different strategies. Each focuses on a different goal (volume, cost control, value volume, value efficiency) and requires a different level of data maturity.
The Smart Bidding overview documentation defines the four core strategies (Target CPA, Target ROAS, Maximize Conversions, Maximize Conversion Value) and states that machine learning performs more reliably on accounts with 30 or more conversions per month. The Target ROAS documentation gives an example minimum threshold for search campaigns of at least 15 conversions in the last 30 days.
What Is Maximize Conversions?
This strategy aims to get the most conversions achievable by spending the full set budget. There’s no fixed cap on cost.
It can be a starting point for new campaigns
For a new campaign without enough historical data, it can be safer to accumulate data with Maximize Conversions first rather than jumping straight into Target CPA.
What Is Target CPA?
Target CPA lets you set the desired average cost per conversion and has the system bid accordingly. It can be applied to a single campaign or to a portfolio strategy spanning multiple campaigns.
The target shouldn’t be set too aggressively
If the target cost is set far below (excessively low relative to) the account’s historical average, the system may fail to bid competitively enough and lose impressions. A realistic starting point is a value close to the account’s actual recent CPA; the real mistake is building the target around a desired number rather than a realistic one.
Avoid changes that disrupt the accumulated data
Major changes such as to the landing page, ad copy, or season can disrupt the pattern the strategy has learned. Expect a performance fluctuation whenever such changes are made; this fluctuation shouldn’t be mistaken for campaign failure.
Maximize Conversion Value and Target ROAS
These two strategies operate on conversion value rather than conversion count, which is why sending accurate value data (such as order amount) is a prerequisite.
If the value data is wrong, the strategy optimizes wrong
The system learns which conversions are more valuable based on the data it receives. If the value data is missing or inaccurate, low-value conversions can end up being optimized as if they were high-value.
The Target ROAS goal should start from historical data
If the target ROAS is set far from the account’s actual recent ROAS, the learning process can take longer. For example, a target ROAS of 500% means aiming for 5 units of revenue per 1 unit of spend; this ratio should be set by comparing it against current performance.
How Should a Strategy Change Be Made?
Moving from manual bidding to Smart Bidding, or from one strategy to another, should be gradual, not sudden.
The learning process needs to be managed patiently
After a strategy change, the system starts learning again. Frequently changing the target during this period, or pausing and restarting the campaign, can keep resetting the learning process.
A portfolio strategy spans multiple campaigns
Multiple campaigns sharing a similar goal can be managed under a single portfolio strategy. This can speed up learning by increasing data sharing across campaigns.
A Recent Note: Naming and Bidding System Changes
In 2026, Google is simplifying the naming of Smart Bidding strategies; instead of combined names like “Maximize conversions with Target CPA” and “Maximize conversion value with Target ROAS,” the plain names “Target CPA” and “Target ROAS” are now used. Additionally, the target bidding change taking effect on August 17, 2026 will affect the bidding system for budget-constrained campaigns; this change may lead to temporary performance fluctuation.
Pre-Launch Checklist
Before choosing a Smart Bidding strategy:
- Is the account’s monthly conversion volume close to the recommended threshold for the chosen strategy?
- If a value-based strategy will be used, is conversion value being sent correctly?
- Was the target (CPA/ROAS) set based on the account’s actual historical performance?
- Is a major landing page or offer change planned in the near future?
A Common Mistake
The most common mistake is setting an aggressive Target CPA or Target ROAS goal before enough conversion data has accumulated. When the system can’t find enough of a pattern to learn from, it either loses impressions or bids inaccurately trying to hit the target.
Summary
Smart Bidding serves different goals through four different strategies (Maximize Conversions, Target CPA, Maximize Conversion Value, Target ROAS). The right choice depends on the account’s data maturity and whether the goal is volume or value. Strategy changes should be made gradually, and the learning process should be managed with patience.