Primary vs Secondary Conversions in Google Ads: How to Set Them Up the Right Way

Of all the settings in Google Ads, the one Ben sees configured incorrectly the most often is also one of the simplest: which conversions are marked as primary and which are marked as secondary. Get it right and Smart Bidding optimises towards real revenue. Get it wrong and the algorithm spends thousands chasing newsletter signups, button clicks, or "Contact Us" page views that never turn into customers.

This guide walks through exactly what each conversion type does, how the bidding algorithm uses them, and the setup Ben uses on every account he manages.

Why this setting matters more than people think

Most advertisers assume "a conversion is a conversion" and tick every action they can track. The problem is that Google Ads doesn't treat every conversion equally. The platform splits them into two buckets:

• Primary conversions are what Smart Bidding optimises towards. Every bid Google places is calculated to generate more of these.
• Secondary conversions are tracked and reported, but Smart Bidding ignores them when setting bids.

If a newsletter signup is marked as primary alongside a £2,000 product purchase, Google treats them as equally valuable optimisation targets. The algorithm will happily pour budget into search terms, audiences, and placements that generate cheap newsletter signups instead of expensive sales. Ben has audited accounts spending £40k a month where the entire bidding signal had been corrupted by misclassified conversions.

What primary and secondary conversions actually are

Google introduced the primary/secondary distinction to give advertisers a way to track lots of useful actions without confusing the bidding algorithm.

Primary conversions are the actions that genuinely represent business value: a sale, a qualified lead, a booked appointment, a phone call lasting more than a defined threshold. These are the events Smart Bidding will work to maximise.

Secondary conversions (sometimes called "observational" conversions) are signals that are useful for diagnostics but shouldn't drive bidding decisions: an Add to Cart event, a video view, a brochure download, a scroll-depth trigger, a button click. They appear in the All Conversions column for analysis, but they don't influence how Google bids.

The split exists because the more conversions you mark as primary, the more diluted your bidding signal becomes. A clean primary list is how Smart Bidding learns what "good" actually looks like.

How Smart Bidding uses each type

Understanding what the algorithm does with each bucket clears up most of the confusion:

• Maximise Conversions bids to generate as many primary conversions as possible within the budget.
• Maximise Conversion Value bids to generate as much primary conversion value as possible (requires conversion values to be set).
• Target CPA bids to keep the cost per primary conversion at the target you set.
• Target ROAS bids to hit a return-on-ad-spend ratio based on primary conversion value.

Secondary conversions show in reporting under "All conversions" but never influence bid calculations. They're useful for spotting upper-funnel signals - if Add to Cart events are climbing but purchases aren't, you have a checkout problem rather than a traffic problem - but they don't change what Google does at auction time.

How to choose your primary conversion

Ben's rule for choosing primary conversions is simple: only mark something as primary if you would happily pay Google to generate more of it.

Apply this test to each conversion action:

1. Does this action correlate directly with revenue, or with a step that almost always leads to revenue?
2. Can the volume be inflated by low-quality traffic? (Newsletter signups, free PDF downloads, and "Contact Us" page views often can.)
3. Would I rather have 100 of these per month or 10 of the next conversion up the funnel?

For most businesses, only one or two conversion actions pass that test. The rest belong in secondary.

What belongs in secondary conversions

Secondary is where the long tail of useful-but-not-primary signals lives. Common examples:

• Add to Cart events
• Begin Checkout events
• View of a key page (pricing, contact, services)
• Newsletter or whitepaper downloads
• Short phone calls (under the qualifying duration)
• Video plays or scroll-depth triggers
• Engaged session events from GA4

Tracking these as secondary keeps them visible in reports without polluting bidding. Ben uses them heavily for diagnosing funnel drop-off but never lets the algorithm chase them.

Account-default vs campaign-level goals

Google Ads lets you set conversion goals at two levels:

• Account-default goals apply to every campaign unless overridden. These are set under Goals > Summary in the conversion settings.
• Campaign-level goals override the defaults for a single campaign. Useful when one campaign has a fundamentally different objective (e.g. a brand awareness campaign optimising towards reach, or a separate lead-gen campaign optimising towards a specific form fill).

Ben's standard setup keeps account-default goals tightly focused on revenue-driving conversions, then overrides them only when a specific campaign has a clearly different objective - never as a workaround for tracking issues.

Step-by-step setup walkthrough

1. Open the conversions dashboard. In Google Ads, go to Goals > Conversions > Summary.
2. Audit the existing list. Note every conversion action, its current category (Purchase, Lead, Page view etc.), its source (Website, Phone calls, Import), and whether it's currently primary or secondary.
3. Identify your true business outcome. For most service businesses this is a qualified lead form or a phone call over 60 seconds. For e-commerce it's a Purchase event with revenue value attached.
4. Set that outcome as primary. Edit the conversion action, change the goal type if needed, and ensure "Primary action" is selected in the Account default goal settings.
5. Move everything else to secondary. Cart adds, page views, micro-engagements - all of these get switched to Secondary so they're tracked but not optimised against.
6. Set conversion values where possible. Even rough lead values (e.g. average deal size × close rate) help the algorithm prioritise higher-quality leads when paired with Maximise Conversion Value or Target ROAS.
7. Verify each campaign. Open every active campaign, check the "Conversion goals" section, and confirm it's using the account default unless there's a deliberate override.
8. Wait at least 14 days before judging the impact. Smart Bidding needs time to retrain on the new signal.

Recommended setup for e-commerce

For most stores Ben works with, the structure looks like this:

• Primary: Purchase (with revenue value passed dynamically through the data layer).
• Secondary: Add to Cart, Begin Checkout, Add Payment Info, View Item, Newsletter Signup.

This setup lets the algorithm chase profitable revenue while still giving Ben full visibility into where customers drop out of the funnel. For stores with very low purchase volume (under 30 conversions/month), Ben sometimes adds Begin Checkout as a temporary primary signal until purchase volume scales, then demotes it back to secondary.

Recommended setup for lead generation

Lead-gen accounts are where Ben sees the most damage from bad conversion setup. The recommended structure:

• Primary: Qualified lead form submission, phone call over 60 seconds, booked appointment.
• Secondary: Generic contact form, newsletter signup, brochure download, short phone calls, "Thank You" page views from non-qualifying forms.

Where possible, Ben pushes offline conversions back into Google Ads from the CRM - tagging which leads became opportunities and which became closed deals. Once that loop is in place, the primary conversion can be upgraded from "lead form" to "qualified lead" or "closed deal", which is where the biggest performance jumps come from.

The most common mistakes Ben sees

1. Marking every conversion as primary. Dilutes the bidding signal and trains the algorithm towards cheap, low-value actions.
2. Tracking only the form submission, not the qualification status. Google ends up optimising for form-fillers regardless of whether they were a fit for the business.
3. Counting "Page view of Contact Us" as a conversion. Easy to inflate, almost zero correlation with revenue.
4. Importing GA4 conversions without categorising them. GA4 events flood in, all get marked primary, and bidding falls apart.
5. Setting conversion values to a flat default like 1. Removes any ability for value-based bidding to prioritise better leads.
6. Switching primary/secondary while in the learning phase. Every change resets the algorithm; batch changes and let them settle for at least two weeks.
7. Counting both a phone call and a form fill from the same user as two conversions. Double-counts the same lead and inflates apparent performance.
8. Not setting account-default goals at all. Each campaign falls back to "all conversion actions", which is the worst possible default.