Using Stock Levels as Bidding Signals in Google Ads
Google Ads doesn't know you have 3 units left. Or 3,000 units you desperately need to move. Here's how to make inventory inform your bidding.
The Inventory Disconnect
Smart Bidding optimises for conversions, not inventory health. It will happily drive traffic to products with 2 units remaining while ignoring products with 2,000 units collecting dust.
This disconnect creates two problems: selling out too fast on popular items (often the wrong items to prioritise in ads) and sitting on slow-moving inventory that ties up capital.
The Commercial Reality
A £50 sale on a product with 500 units in stock is worth more than a £50 sale on a product with 5 units remaining. One helps cash flow; the other just accelerates a sellout.
Stock as a Bidding Signal
Inventory levels should influence bidding in several ways:
- High stock: Bid more aggressively to move inventory before it ages
- Low stock: Reduce bids or pause to preserve inventory for higher-value channels
- Overstock: Consider promotional bidding to accelerate clearance
- Out of stock: Pause advertising entirely to avoid wasting spend and frustrating customers
The goal isn't just to sell; it's to sell the right things at the right time.
Implementation
Three approaches to implementing stock-aware bidding:
- Custom labels in feed: Add stock tier labels (high/medium/low/out) to your product feed and use them to segment campaigns with different bid strategies.
- Automated feed rules: Use feed rules to exclude or suppress products below a stock threshold.
- Scripts with inventory API: Build scripts that pull inventory data and adjust bids or budgets based on stock levels.
Start Simple
Begin with feed exclusions for out-of-stock and low-stock products. This single change often improves POAS significantly before you add more sophisticated logic.
Setting Thresholds
Stock thresholds should reflect your business realities:
- Lead time: How long does replenishment take?
- Sales velocity: How fast does the product typically sell?
- SKU importance: Is this a hero product that needs protection?
- Seasonality: Will demand increase before restocking is possible?
A "low stock" threshold of 10 units makes sense for a product selling 2/day with 3-day restocking. It makes no sense for a product selling 50/day with 2-week lead times.
Automation Options
For larger catalogues, manual management becomes impossible. Consider:
- Feed management tools with inventory rules
- Google Ads scripts that sync with inventory systems
- Third-party bid management platforms with inventory integration
- Custom middleware that updates feeds based on real-time stock
Watch for Lag
Stock data in Google Ads often lags behind reality. If your feed updates daily but stock changes hourly, you'll advertise out-of-stock products. Build in safety buffers.
Next Steps
Audit your current setup: are you advertising products you can't fulfil? Are high-stock products getting the visibility they need?