Google Ads Smart Bidding uses machine learning to set bids in real time for every auction. For many advertisers it delivers better results than manual bidding. For others it burns through budget while the algorithm “learns”. Knowing how Smart Bidding works, and when it tends to struggle, will save you time and money.
What Smart Bidding Is
Smart Bidding is the group of automated bid strategies that optimise for conversions or conversion value. The main options are:
- Target CPA (tCPA). Bids are set to achieve your target cost per acquisition. Google bids more when a click looks likely to convert and less when it does not.
- Target ROAS (tROAS). Bids are set to hit a target return on ad spend. This suits e-commerce accounts where order values vary.
- Maximise Conversions. Google spends your budget to get as many conversions as possible. You can add an optional target CPA.
- Maximise Conversion Value. Google aims for the highest total conversion value within budget. You can add an optional target ROAS.
Smart Bidding needs accurate data to work. Poor conversion tracking produces poor bidding, so set tracking up properly first. Our guide on how to track conversions in Google Ads covers the setup.
The Pros of Smart Bidding
Smart Bidding weighs many signals at auction time, including device, location, time of day, audience list membership, and the search query itself. A person adjusting bids in a spreadsheet cannot match that level of real-time adjustment.
It also saves management time. Instead of revisiting bid modifiers every week, you can spend that time on creative, landing pages, and audience strategy, where human judgment still adds the most value.
Results depend on the account, so your own before-and-after comparison matters more than any benchmark. Run the switch as an experiment, which Google Ads supports through campaign experiments, and compare cost per conversion over the same period.
The Cons of Smart Bidding
The main risk is the learning period. Changes such as a new target, a big budget change, or a conversion goal edit restart learning, and cost per acquisition often swings while the system recalibrates. Google suggests waiting at least two weeks without changes for the initial learning period. If you change targets frequently or run a small budget, the algorithm may never settle.
Volume matters too. For target-based strategies, Google’s guidance cites a minimum of about 15 conversions in 30 days and recommends 30 or more. Below that, bids rest on thin evidence.
Smart Bidding also chases whatever you tell it to count. If newsletter sign-ups and purchases are both counted as conversions with equal weight, the algorithm will happily deliver cheap sign-ups. Separate your primary conversion actions from secondary ones before you switch.
When to Use Smart Bidding
Smart Bidding makes sense when:
- The campaign records 30 or more conversions per 30 days with accurate tracking
- Conversion values are reliable and you know your margins
- Budgets are steady and you are not restructuring the account every week
- Demand is reasonably stable rather than swinging sharply
For seasonal peaks such as Black Friday, avoid big changes in the weeks right before the peak so the algorithm enters your key period in a settled state. If you plan to change strategy, do it early enough to complete the learning period first.
When to Start with Manual CPC
New campaigns with no conversion history can start on manual CPC or Maximise Clicks while they collect data, then move to Maximise Conversions and later a target-based strategy. Enhanced CPC used to be the middle option, but Google removed it from Search and Display campaigns in March 2025, and campaigns still using it moved to manual CPC. Maximise Conversions with no target is now the usual first step into automation.
Accounts where margin varies a lot between products may also do better with bids set by product group, since the algorithm only sees the value data you give it. Feeding margin into conversion value solves part of that problem.
It also helps to understand how the Google Ads auction works, because every bid decision happens at the moment of each auction. A higher Google Ads Quality Score lowers the CPC you need to pay for the same position. If you run Shopping campaigns, our comparison of Performance Max and Standard Shopping shows how bidding interacts with campaign type.
Making the Switch
When you move to Smart Bidding, set the first target close to your average CPA or ROAS over the past 30 days. A target far below what the account has ever achieved can leave the campaign entering very few auctions. After the initial two-week learning period, judge performance over a 30-day window and allow for conversion delay in the most recent days. Change one thing at a time so you know what caused any shift. If results slip, check your conversion tracking before blaming the strategy.
Frequently Asked Questions
How many conversions do I need for Target CPA?
Google’s guidance cites at least 15 conversions in the last 30 days as a minimum, with 30 or more recommended for stable results.
How long is the Smart Bidding learning period?
Google advises allowing at least two weeks without changes for the initial learning period, though complex accounts can take longer to settle.
Should I use Maximise Conversions or Target CPA first?
Many advertisers start with Maximise Conversions to gather data, then add a target CPA once costs are stable and volume is high enough.
Smart Bidding works well when the conditions are right, and the skill lies in knowing when they are. If you want a second pair of eyes on your account, see our Google Ads management service.