A primary conversion is a conversion action in Google Ads that is counted in the main Conversions column and that automated bidding is allowed to optimise towards. Every conversion action you create is set to either primary or secondary, and that single setting decides whether the action steers your spend or is simply recorded.
How a primary conversion works
Each conversion action sits inside a goal, such as Purchases, Submit lead forms or Phone call leads. Within the goal you mark each action as primary or secondary. Primary actions feed the Conversions, Conv. value and Cost / conv. columns. Secondary actions appear only in the All conversions columns, where you can see them without them shaping bids.
Campaigns use goals in one of two ways. By default they follow the account-default goals, so every primary action in those goals counts for every campaign. Alternatively, a campaign can have its own campaign-specific goals, which lets a brand campaign work towards phone calls while a Shopping campaign works towards online purchases.
When a Smart Bidding strategy such as Maximise conversions or Target ROAS runs, it learns from the primary actions in the goals that campaign uses. Secondary actions in the same goal are watched but not optimised for.
Why it matters
Automated bidding does exactly what the primary actions tell it to. If a newsletter sign-up and a £3,000 kitchen enquiry are both primary and carry the same value, the system will chase the cheaper sign-ups because they are easier to win. Cost per conversion looks excellent and the phone stays quiet.
This is a common reason a UK account looks healthy in the dashboard and disappointing in the bank account. A plumbing firm in Leeds that counts every tap on its phone number alongside calls that lasted over a minute, or a retailer that counts add to basket as primary, is giving the algorithm the wrong target.
Reporting suffers as well. The Conversions column is the number most owners read first, and every extra primary action inflates it, so decisions about budget get made on a figure that does not match sales.
Common mistakes
- Leaving every imported GA4 event as primary, including page views and scroll depth.
- Counting the same sale twice, once from the Google tag and once imported from GA4, with both set to primary.
- Making micro-actions such as brochure downloads primary in a campaign that should be bidding for revenue.
- Changing which actions are primary every few days. Each change shifts what the bidding learns from, and results wobble while it adjusts.
- Forgetting that campaign-specific goals override the account defaults, so an account-level change does nothing for that campaign.
How to act on it
Open Goals, then Conversions, then Summary, and list every action with its goal and status. Ask one question about each: if I got more of these and nothing else, would the business be better off? Only actions that pass should be primary. Everything else can stay as a secondary conversion for insight.
Then look at values. If you sell online, pass the real basket value. If you take enquiries, give each primary action a value that reflects what it is typically worth, so the system can tell a quote request from a brochure request. Before trusting any of this, check that each action fires once per real event; my guide on testing whether your conversion tracking works walks through the checks. Setting goals so bidding chases the right outcome is one of the first jobs in my Google Ads management work.