Bidding Strategies for Google Shopping

Your bidding strategy determines how much you pay for each Shopping click and how aggressively you compete in the auction. The right strategy depends on your data volume, business goals, and level of control needed. This guide covers every available bidding strategy for Shopping campaigns and explains how CSS interacts with each one.

Manual CPC

Manual CPC gives you direct control over the maximum bid for each product group. You set the bid, and Google will not exceed it. The actual CPC you pay is determined by the auction and is typically lower than your maximum bid.

When to use it: Manual CPC makes sense when you have very specific bid requirements, are managing a small catalog where individual bid management is feasible, or when you are collecting initial conversion data before switching to automated strategies. It is also useful for testing new product categories where you want to control spend tightly.

Limitations: Manual CPC does not optimize at the query level. The same bid applies to every search query that matches a product group, regardless of the user's intent or likelihood of converting. This is a significant limitation in Shopping, where query intent can vary enormously for the same product.

CSS interaction: With Manual CPC, the CSS advantage is straightforward. Your bids become approximately 20% more competitive in the auction because the Google Shopping Europe margin is removed. You will see higher ad positions at the same bid or can reduce bids by approximately 20% to maintain the same positions at lower cost.

Enhanced CPC (ECPC)

Enhanced CPC is a semi-automated strategy that starts with your manual bids but adjusts them up or down for individual auctions based on the likelihood of conversion. Google's algorithm increases bids for queries that are more likely to convert and decreases bids for less promising queries.

When to use it: ECPC is a transitional strategy for advertisers moving from Manual CPC to fully automated bidding. It provides some auction-level optimization while maintaining your manual bid as a baseline. It requires conversion tracking to be set up and working correctly.

Limitations: ECPC has become less relevant as fully automated strategies have improved. Google's recommendation has shifted toward Target ROAS or Maximize Conversions for most advertisers. ECPC's adjustments are also more limited than those made by fully automated strategies.

CSS interaction: Similar to Manual CPC. The CSS advantage improves the effective competitiveness of every bid, and ECPC's adjustments operate on top of the improved baseline. The net effect is better performance at each adjustment level.

Target ROAS (Return on Ad Spend)

Target ROAS is the most popular bidding strategy for mature Shopping campaigns. You set a target return on ad spend (for example, 500%, meaning 5 euros in revenue for every 1 euro spent on ads), and Google's algorithm adjusts bids to achieve that target across the campaign.

How it works: The algorithm evaluates each auction opportunity based on the user's search query, device, location, time of day, audience signals, and dozens of other factors. It predicts the likelihood and value of a conversion, then sets a bid that aligns with your ROAS target. For high-value queries, it bids aggressively. For low-value queries, it bids conservatively or does not bid at all.

When to use it: Target ROAS is ideal when you have consistent conversion data (at least 15 to 20 conversions per month per campaign) and a clear understanding of your target return. It works best for established campaigns with stable performance histories.

CSS interaction: This is where CSS and Smart Bidding create a powerful combination. When you switch to an independent CSS like Cobiro, the algorithm detects improved auction efficiency within a few days. It then recalibrates bids to take advantage of the improved economics. In practice, Target ROAS campaigns see one of two outcomes after a CSS switch: the same ROAS target is hit at lower total spend, or the same spend achieves a higher actual ROAS. Either way, the economics improve. For detailed calculations, see Calculating Real Savings.

Maximize Conversions

Maximize Conversions aims to get the most conversions possible within your daily budget. The algorithm sets bids to maximize the total number of conversions, without a specific CPA or ROAS constraint.

When to use it: This strategy is useful when your primary goal is volume (for example, acquiring new customers at scale) and you are less concerned about the cost per acquisition. It is also a good starting point for new campaigns that need to build conversion history before switching to Target ROAS.

Limitations: Without a ROAS or CPA constraint, Maximize Conversions may spend more per conversion than you would like. It prioritizes volume over efficiency. Monitor CPA and ROAS closely to ensure profitability.

CSS interaction: With CSS reducing the effective cost per click, Maximize Conversions can acquire the same number of conversions at lower total cost, or acquire more conversions within the same budget. The algorithm simply has more purchasing power in each auction.

Maximize Conversion Value

Maximize Conversion Value aims to maximize the total revenue (or other conversion value) generated within your budget. Unlike Maximize Conversions, which treats all conversions equally, this strategy prioritizes higher-value conversions.

When to use it: This is the recommended strategy for e-commerce advertisers who want to maximize revenue. It is the budget-constrained version of Target ROAS. If you have a fixed budget and want the most revenue possible from it, Maximize Conversion Value is the right choice.

CSS interaction: The CSS advantage translates directly into higher conversion value for the same budget. With 20% lower CPCs, the same budget reaches more high-value auctions, resulting in higher total revenue. This is particularly impactful for advertisers with strict budget constraints.

Portfolio Bidding Strategies

Portfolio strategies apply a single bidding strategy across multiple campaigns. Instead of setting a Target ROAS for each campaign individually, you create a portfolio strategy with a single target that optimizes across all linked campaigns as a group.

Benefits: Portfolio strategies pool data from multiple campaigns, giving the algorithm more signals to work with. This is particularly valuable for campaigns with lower individual conversion volumes. By combining campaigns into a portfolio, each campaign benefits from the learnings of the others.

Use cases:

• Multiple Shopping campaigns targeting different product categories with the same ROAS target
• A standard Shopping campaign and a Performance Max campaign sharing a Target ROAS
• Campaigns in different markets (countries) with similar business objectives

CSS interaction: Portfolio strategies work identically with CSS. The improved auction economics from CSS apply to all campaigns in the portfolio, and the algorithm optimizes across the combined data set with the improved cost structure.

Common Bidding Mistakes

Even experienced advertisers make bidding errors. Here are the most common mistakes and how to avoid them.

Setting Target ROAS Too High Initially

If you set an aggressive ROAS target from the start, the algorithm will severely restrict spending to avoid missing the target. This results in very low impression share and minimal data collection, creating a negative feedback loop. Start with a realistic target based on historical performance and increase gradually.

Not Enough Conversion Data

Smart Bidding strategies need sufficient conversion data to optimize effectively. Google recommends at least 15 conversions per month per campaign for Target ROAS, though 30 or more provides a more stable signal. If your campaign does not generate enough conversions, consider using Maximize Clicks to build volume first, or consolidate campaigns to pool data.

Ignoring Impression Share

Low impression share means you are missing opportunities. If your impression share is below 50%, your products are only appearing in half the auctions they are eligible for. This could indicate that your bids are too low, your budget is too constrained, or your feed quality needs improvement. Monitor impression share alongside CPC and ROAS.

Manual Bid Changes After CSS Switch

After switching to CSS, do not manually lower your bids. Smart Bidding algorithms detect the improved auction efficiency and adjust automatically. Manually lowering bids disrupts the algorithm's learning and can cause performance dips. Let the system recalibrate naturally over one to two weeks.

Using the Same Strategy for All Products

Different product segments may warrant different bidding approaches. High-margin bestsellers might benefit from aggressive bidding, while low-margin accessories might need conservative targets. Use custom labels to segment products and consider separate campaigns or portfolio strategies for different margin tiers.