Bidding in ChatGPT Ads explained: max bid, CPC vs. CPM and the “often outbid” signal

ChatGPT Ads assigns placements by auction: for every matching conversation, all ads that fit the request compete, and the max bid helps decide who gets shown. Unlike Google Ads, there are no automated bidding strategies yet — you set a maximum bid per ad group. That makes it all the more important to understand exactly what that number means.

The max bid applies per billing event

The maximum bid always refers to the event the campaign bills for: a single click under click billing, a single impression under impression billing. In the Ads Manager and in Chatvertise you enter CPM bids per 1,000 impressions as usual — internally, though, the API counts per impression. Anyone setting bids directly through the API can be off by a factor of 1,000 here. Chatvertise converts the value correctly depending on the billing model and shows CPC and CPM bids with their unit in every table.

The billing model is a campaign decision

Whether you're billed per click or per impression is set when the campaign is created — permanently. Every ad group inherits this model; the API rejects an ad group with a different billing event. That's why Chatvertise locks the field in the ad group form to the campaign's value. If you want to move from CPM to CPC, cloning the campaign is the only way — there's a separate article on that in the blog.

What “you're often outbid” means

The OpenAI Ads Manager flags some ad groups with a note that the bid is too low and frequently outbid. That note is purely auction-based: there's no absolute threshold below which a bid is “too low” — the same bid can be enough in a niche and hopeless in a competitive category. The API doesn't currently expose this signal; Chatvertise therefore deliberately links to the Ads Manager instead of faking a heuristic of its own.

Optimizing bids: a practical approach

• Start with a bid you can afford per click: target cost per conversion × expected conversion rate. With a $40 target CPA and a 2% conversion rate, that's $0.80 per click.
• No impressions after 24 to 48 hours? Raise the bid in steps of 15 to 20%, don't double it — every increase needs a day of data.
• Watch CTR and CPC in Chatvertise: if CPC rises without conversions following, the bid is above what a click is worth.
• Set an automation rule as a safety net, for example “CPA over 7 days above $60 → pause campaign”.
• Split ad groups by value: high-margin products can carry a higher bid than entry-level products — one bid per ad group allows exactly that.

CPM, CPC or conversions?

Impression billing pays off for reach and brand awareness, click billing for traffic with predictable costs, conversion optimization only once tracking is live and conversions arrive regularly. When in doubt: start with CPC, collect data, then decide.