ChatGPT Ads Bidding and Budgets: CPM, CPC and Conversion Optimization

You set a daily budget of $100, and Tuesday's report shows $180 in spend. That's not an error: in ChatGPT Ads, the daily budget is an average, not a hard cap for each day.

This is one of several rules that set ChatGPT Ads bidding and budgets apart from familiar platforms. Below, we cover how the auction works, which strategy to choose, and how to budget your first test.

How the auction works

Impressions are won in a relevance-weighted, second-price auction. This means a more relevant ad can win an impression even over an ad with a higher bid.

Relevance depends on the conversation context, ad copy, landing page, and context hints. So raising your bid isn't the only way to get more impressions, and not always the best one. We cover how to improve relevance in this article.

Ads Manager shows how competitive your bid is. This is guidance, not a restriction: an ad with a "weak" bid still enters the auction. Right after you change an ad group, this guidance may not appear, since it isn't shown for the first 24 hours.

Three objectives and how you pay for them

The objective is set at the campaign level and can't be changed after creation.

With the Conversions objective, the system looks for clicks that are more likely to lead to the target action. You pay per click, not per conversion. Clicks here may cost more than in a Clicks campaign, so compare the final cost per conversion.

What counts as a conversion for optimization

A conversions campaign optimizes for exactly one standard event, such as a purchase (order_created) or a lead (lead_created). Custom events can't be used for optimization. The event is chosen when the campaign is created and can't be changed later.

A conversion is counted if the action happens within the attribution window: up to 30 days after a click by default, or within 1 day after an impression. We cover events, windows, and pixel setup in detail in the article "ChatGPT Ads conversion tracking".

Fixed bid or Maximize results

Bids are set at the ad group level. There are two strategies.

Fixed bid. You set the maximum price per click or per thousand impressions. It works with all three objectives and with both daily and lifetime budgets. Custom audience bid adjustments, from 0.1× to 10×, work only with this strategy.

Maximize results. The system sets bids automatically to get as many clicks (Maximize clicks) or conversions (Maximize conversions) as possible within your budget. You don't set a maximum bid. This strategy requires a daily budget and, for conversions, one active standard event.

You can switch an existing ad group from a fixed bid to Maximize results by removing the bid, as long as the campaign has a daily budget. Audience bid adjustments are cleared in the process, and you'll need to set them again if you switch back to a fixed bid.

How much to bid

For cost-per-click campaigns, OpenAI recommends starting at $3–5 per click. OpenAI's public documentation has no CPM recommendation.

The platform doesn't have benchmarks yet, as OpenAI states in its help center. In our first test in Cyprus, the average CPC was $1.63 with a 0.64% CTR. This is an early indicator from one market and one creative, not a benchmark: the auction there is small. Learn more in our case study.

Budgets: daily and lifetime

A campaign can have one of two budget types:

• daily: average spend per day, with a $25 minimum for USD accounts and different minimums for other currencies;
• lifetime: a cap for the entire campaign duration, available only with a fixed bid.

You can replace a lifetime budget with a daily one, but not the other way around: that requires a new campaign. A lifetime budget can't be reduced below the amount already spent.

Why daily spend can exceed the budget

The daily budget is an average spending target over a seven-day period, not a strict daily spending cap. Spend is paced throughout the day, but on some days it can exceed the budget. The limits are:

• no more than two daily budgets in a single day;
• no more than seven daily budgets in a Sunday-to-Saturday week.

With a $100 daily budget, Tuesday's spend could reach $180, but weekly spend won't exceed $700. Days follow the account's time zone.

For conversions campaigns, OpenAI specifically notes that the system aims to improve results, not necessarily to spend the full budget. Underspend in these campaigns is normal.

Account-level limits

Some accounts have a spend limit for a set period. It caps total spend across all campaigns, regardless of their budgets. Once the limit is reached, delivery stops in every campaign in the account.

How to budget your first test

Work backward from the number of clicks you need to draw conclusions. Example calculation:

• goal: 30 clicks per day;
• bid: $4 per click, the middle of OpenAI's range;
• daily budget: 30 × $4 = $120;
• two-week test: about $1,680.

If you optimize for conversions, your budget should give the system enough target actions to learn from. If conversions are scarce, start with the Clicks objective and set up event tracking: conversion data will build up for the next stage.

How to change bids and budgets

• Change one setting at a time and note when you made the change. Otherwise, you won't know what affected the results.
• Don't evaluate a change on the same day. Spend appears with a delay of up to 7–8 hours, and bid strength guidance doesn't appear for the first 24 hours after you edit an ad group.
• Check your bids when lowering the daily budget. The system may reject a budget that's lower than the ad group's bid.
• Raise bids only after checking relevance. If your hints and ad describe a rare situation, a higher bid won't create more matching conversations.

Key takeaways on bidding

In ChatGPT Ads, money isn't the only lever. A relevant ad wins the auction for less, so work on hints and creative directly affects your cost per click.

For a first test, a fixed bid on clicks and a budget for 2–3 weeks is enough. Switch to Maximize results and the Conversions objective once you've collected event data.

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