Smart Bidding is Google Ads' portfolio of automated bid strategies that use machine learning to optimise bids in real time for every auction. Instead of setting a fixed maximum CPC, Smart Bidding strategies dynamically adjust bids based on dozens of signals — device, location, time of day, audience, query context, and more — to achieve a specific performance goal. The main Smart Bidding strategies are Target CPA (target a specific cost per acquisition), Target ROAS (target a specific return on ad spend), Maximise Conversions, and Maximise Conversion Value.
Smart Bidding has become the standard approach for most Google Ads campaigns as Google's machine learning has improved significantly. Manual CPC bidding — setting specific bids for individual keywords — remains appropriate for new campaigns without conversion data, very small budgets, or campaigns where precise bid control is commercially necessary. For most established campaigns with sufficient conversion data, Smart Bidding typically outperforms manually set bids.
Smart Bidding strategies compared
- Target CPA — sets bids to achieve a target cost per conversion; requires sufficient conversion data (50+/month) to work effectively
- Target ROAS — sets bids to achieve a target return on ad spend; for ecommerce with revenue values on conversions
- Maximise Conversions — spends the full budget to get the maximum number of conversions; no CPA target
- Maximise Conversion Value — maximises total conversion value within budget; no ROAS target
- Enhanced CPC (eCPC) — manual CPC with automatic adjustments for higher-converting situations; a bridge between manual and full Smart Bidding
- Target Impression Share — maintains a target percentage of auctions where your ad is shown; more appropriate for brand visibility than performance goals
Google recommends at minimum 30 conversions per month within the campaign (preferably 50+) before switching to Target CPA or Target ROAS bidding. Below this threshold, the machine learning model has insufficient data to make accurate bid predictions, resulting in erratic performance. During the learning phase (typically two to four weeks after switching strategies), expect some performance variability as the model adjusts. New campaigns without conversion history should start with Maximise Conversions to accumulate data before switching to Target CPA.
Yes — Smart Bidding can underperform or cause budget waste in several situations: insufficient conversion data (the model makes poor predictions), incorrect conversion tracking (optimising toward the wrong events), seasonal spikes the model has not seen before, target CPA or ROAS targets set unrealistically low (forcing the algorithm to heavily restrict impressions to meet the target), and campaigns with very small budgets where the model lacks spend volume to learn effectively. Monitoring Smart Bidding campaigns closely in the first four to six weeks and adjusting targets based on actual performance is essential.