What's the difference between average and maximum cost bidding?
If you're creating an advert set that meets the following criteria, you can choose between average cost bidding and maximum cost bidding:
Optimised for conversions or app installs
Getting charged for impressions
Using manual bidding
Whichever you choose, we try to keep your average cost at or below your bid.
If you can't decide which to use, consider the following guiding principles:
If you care more about maximising delivery and conversion volume within an average cost threshold, you should probably use average cost bidding.
If you care more about every result you're optimising for costing no more than a given amount, you should probably use maximum cost bidding.
Average cost bidding
Average cost bidding allows you to tell us what you want your average cost per result to be, rather than the maximum amount that you're willing to pay for any given result.
If you use this type of bidding, we'll try to get you as many results as possible while keeping your average cost per result less than or equal to your desired average. The cost for a given individual result might be more or less than this average, but over time, as you accumulate more results, the average cost for each should even out to this number or less.
Important: We measure your average cost per action based on one-day or seven-day post-click attribution windows (depending on which you choose to optimise for during advert set creation) in adverts reporting. If you're not using a one-day or seven-day post-click attribution window in your adverts reporting, the results you see might not match the delivery you're getting. Learn how to change your attribution window.
For example, if you set your average cost per app install at £10, we'll show your advert to people who are likely to install your app. Sometimes we may need to spend £8 to find someone to install your app, and other times we may need to spend £12, but over time we'll aim to have your charges average out to £10 per app install, starting from the time you set your bid to £10.
In the example below, imagine that you have a budget of £50 and set your average cost bid at £10.
Enlarge
In this scenario, you'd spend £48 of your budget for six results at an average of £8 each.
Note: You can't choose accelerated delivery for an advert set using average cost bidding. This is because accelerated delivery involves entering your max bid into as many auctions as possible as quickly as possible, so it's not compatible with how we approach delivering your advert set when optimising for your desired average cost. Learn more.
Maximum cost bidding
Maximum cost bidding allows you to tell us the maximum amount that you're willing to pay for a result. If you use this type of bidding, we'll try to get you as many results as possible at a price that's equal to or less than your bid. However, in limited cases, costs may end up being greater than your bid. For example, this might happen if we overestimate how many people will convert through your advert early in your campaign before we've gotten data on its performance and try to make up for that, or with advert sets that have smaller budgets and infrequent conversions or app installs.
Tip: We generally recommend going for a higher budget for these advert sets, even if this means that you have to lower your bid. It's important to get a least a few results a day for your advert set so that we can start gathering information on your advert and refine how we show it.
In the example below, imagine that you have a budget of £50 and set your maximum cost bid at £10.