"Should I use Maximize Conversions or Target CPA?" is one of the questions I hear most from business owners running their own Google Ads. The bidding menu looks like a list of competing options, but in current Google Ads the strategies are really two families with an optional target on top.
In this guide I explain how Smart Bidding works, what each strategy actually optimises for, how the learning period behaves, and how I choose a strategy for lead generation and ecommerce accounts.
What is Smart Bidding in Google Ads?
Smart Bidding is the group of Google Ads bid strategies that use machine learning to set a bid for each individual auction, based on how likely that auction is to lead to a conversion or conversion value. It is sometimes called auction-time bidding, because the bid is calculated in the moment rather than set by you per keyword.
To predict conversion likelihood, Smart Bidding looks at signals such as device, location, time of day, the search query, audience membership, browser and language. You never see these calculations, which is why the quality of your conversion data matters so much: it is the only feedback the system receives.
Not every automated strategy is Smart Bidding. Maximize Clicks and Target Impression Share are automated, but they optimise for clicks or visibility, not conversions. Enhanced CPC, an older semi-automated option, has been phased out for most campaign types.
How do the main Smart Bidding strategies compare?
The core Smart Bidding strategies are Maximize Conversions and Maximize Conversion Value, and each can run with or without a target. Adding a target turns them into what used to be called Target CPA and Target ROAS.
| Strategy | Optimises for | Optional target | Best fit |
|---|---|---|---|
| Maximize Conversions | The most conversions within your budget | Target CPA (cost per action) | Lead generation where every lead is roughly equal |
| Maximize Conversion Value | The most total conversion value within your budget | Target ROAS (return on ad spend) | Ecommerce, or leads with reliable different values |
Target CPA tells Google the average cost per conversion you want. Target ROAS tells it the average conversion value you want for each unit of spend, expressed as a percentage. Both are averages, so some individual conversions will cost more and some less.
Maximize Conversions
Maximize Conversions without a target tries to spend your full daily budget and get as many conversions as possible. That makes it a good starting point for a new campaign that has little history, because it does not need to hit a cost goal. The downside is that it can spend the whole budget even when conversions get expensive.
Maximize Conversions with a target CPA
Adding a target CPA asks Google to keep the average cost per conversion near your target. It may spend less than your budget if it cannot find conversions at that cost. A target set far below what the campaign has historically achieved usually leads to much lower volume, not cheaper leads.
Maximize Conversion Value
Maximize Conversion Value tries to get the highest total conversion value from your budget. It only makes sense when conversion values are accurate, such as real order values from an ecommerce site. If every conversion has the same value, it behaves much like Maximize Conversions.
Maximize Conversion Value with a target ROAS
Adding a target ROAS asks Google to hit an average return. If you set it to 400%, you are asking for four units of conversion value for every unit spent. As with target CPA, an aggressive target restricts volume.
What is the Smart Bidding learning period?
The learning period is the time after you launch or significantly change a bid strategy when Google is recalibrating, and performance can be less stable. The bid strategy status shows "Learning" while this happens.
How long it lasts depends mainly on how many conversions the campaign gets and how long people take to convert after clicking. A campaign with plenty of daily conversions learns quickly. A campaign with a handful of conversions a month learns slowly, and may never stabilise properly.
Things that typically restart or extend learning:
- Switching to a different bid strategy
- Large changes to a target CPA or target ROAS
- Big budget changes
- Changing which conversion actions the campaign optimises for
- Major structural changes, such as merging ad groups or campaigns
My rule is to make one meaningful change at a time and judge results over a period that covers your normal conversion delay, not over two days.
How much conversion data does Smart Bidding need?
Smart Bidding needs enough conversions for the algorithm to spot patterns, and more is always better. Google does not publish a strict minimum for most strategies, but in practice campaigns with very few conversions behave erratically, while campaigns with steady weekly conversions are far more predictable.
If your volume is low, you have options:
- Consolidate. Fewer, larger campaigns pool data. I cover this in my post on Google Ads account structure.
- Use portfolio bid strategies. A portfolio strategy shares one bid strategy, and its data, across several campaigns.
- Optimise for a slightly earlier but still meaningful action, such as a qualified form submission, rather than a closed deal that happens rarely.
- Start without a target and add one once you have stable history.
What you should not do is mark soft actions, like button clicks or page views, as primary just to increase volume. Smart Bidding will deliver more of them, and they will not be customers.
How do I choose the right bid strategy?
Choose based on what your conversions represent and how much history you have. This is the decision path I follow.
- Is conversion tracking accurate? If not, fix it first. Smart Bidding on broken tracking is worse than manual bidding. My guide to setting up Google Ads conversion tracking with GTM covers the basics.
- Do conversions have meaningful, different values? If yes, use Maximize Conversion Value. If they are all roughly equal leads, use Maximize Conversions. For Todays Deal BD, verified purchase values had to reach Google Ads before ROAS-driven bidding made sense.
- Does the campaign have stable conversion history? If no, run without a target. If yes, consider adding a target close to what you have been achieving.
- Do you need to protect profitability? Set a target CPA or target ROAS based on your real margins, then move it gradually rather than in big jumps.
For local service businesses, I often start with Maximize Conversions on a well-structured Search campaign, then add a target CPA once lead volume and cost are stable. Feeding qualified leads back through offline conversion tracking lets bidding learn which leads become jobs, and opens the door to value-based bidding later.
What tools help you control Smart Bidding?
Beyond targets and budgets, Google Ads offers a few tools that help in specific situations:
- Seasonality adjustments: tell Smart Bidding to expect a short-term change in conversion rate, such as a flash sale.
- Data exclusions: tell it to ignore a period when tracking was broken, so bad data does not distort learning.
- Conversion value rules: adjust values based on location, device or audience when certain customers are worth more.
- Campaign-specific conversion goals: choose exactly which conversion actions each campaign optimises toward.
- Bid strategy reports: show the strategy's status, its top signals and how targets compare to results.
Data exclusions are the one I use most, because tracking outages happen in real accounts, and letting a week of zero conversions feed the algorithm can cause bids to drop sharply.
Final thoughts
Smart Bidding is only as good as the conversions you tell it to chase, so the real work is clean tracking, sensible structure and patient targets. If you would like help choosing and setting up the right strategy, take a look at my Google Ads management service or book a free audit.
