What Meta says
In Meta's own words: “Cost per result goal is a goal-based bid strategy that helps you maximize results from your campaign while controlling your average cost.” (Meta help center)
The right control for a cost target
If what you actually want is a cost per acquisition, cost cap is the strategy that aims at it. You give Meta the average cost you are targeting and it manages bids across auctions to hit that on average, rather than the bid cap approach of capping every individual bid. It is a cost control; a bid cap is not.
What to expect
Cost cap trades some volume for cost stability, and like any conversion strategy it needs enough events to work, so a cost target set unrealistically low can starve delivery the same way a tight bid cap does. Set the target where the account can actually clear it, and give it room through the learning phase.
A worked example
Say an ad set's cost per purchase over the past 30 days is $50. Meta's guidance is to start the cost per result goal 10 to 20% higher, so $55 to $60. Expect some days at $70 and some at $45; what Meta aims to hold near the goal is the weekly average, so judge it after at least 7 days, not after one expensive afternoon.
Common questions
Is cost per result goal the same as cost cap?
Yes. Meta now labels cost cap as cost per result goal in Ads Manager; the mechanic, an average cost target that Meta bids dynamically toward, is the same.
What is the difference between cost cap and bid cap on Meta?
A cost cap targets an average cost per result and lets Meta bid dynamically to reach it. A bid cap sets a fixed ceiling on the bid in each auction and does not target a cost. For a cost goal, use cost cap.
Is cost cap better than bid cap?
For most advertisers aiming at a cost target, yes, because it controls the outcome you care about. Bid cap is better only when you can calculate the precise bid from a known conversion rate.
What is cost cap bidding?
Cost cap, shown in Ads Manager as cost per result goal, is a Meta bid strategy where you set a target average cost per result and Meta bids higher or lower per auction to maximize conversions while keeping the weekly average near that goal. Meta notes adherence is not guaranteed.
How do I choose a cost per result goal amount?
Meta recommends starting 10 to 20% above your recent average cost per result. With no history, run the highest volume bid strategy for at least 2 weeks and use the resulting cost per result as your starting value.
How many conversions does cost per result goal need?
Meta says it works best with at least 50 to 100 conversions per week per ad set. Below that, Meta suggests broadening the audience, increasing the budget, or raising the goal.