Use lowest cost (highest volume) while an account or campaign is learning and needs purchase data. Switch to a cost cap set near your target CPA once a campaign gets around 30 or more purchases a week, so Meta stops spending on expensive conversions. If a cost cap stops delivery, raise it in steps of 10 to 20% rather than removing it.
How each strategy works
| Strategy | What Meta does | Best for |
|---|---|---|
| Lowest cost (highest volume) | Spends the full budget and gets as many results as possible | Learning, testing, low data |
| Cost per result goal (cost cap) | Tries to keep average cost near your cap, may underspend | Scaling profitably |
| ROAS goal (minimum ROAS) | Targets a minimum return on each auction | Brands with varied order values |
| Bid cap | Caps each auction bid | Advanced, tight control |
Where to set a cost cap
Start at your target CPA, or slightly above your recent average CPA if that's lower. Setting it far below what the account currently achieves usually just stops spend.
What to do if delivery stops
- Wait 24 to 48 hours; delivery often ramps slowly.
- Raise the cap 10 to 20%.
- Check creative: weak ads can't win auctions at a capped price.
Our rule of thumb
Lowest cost to find winners, cost cap to scale them. Pair a cost-capped scale campaign with a lowest-cost testing campaign.
Break-even CPA calculator
Frequently asked questions
Why is my cost cap campaign not spending?
The cap is likely below what Meta can achieve with your current creative and audience. Raise it gradually, or improve the creative.
Should I use a cost cap on a new campaign?
Usually not. New campaigns need data, and a cap can starve them. Start with lowest cost, then add a cap once purchases are steady.
Is minimum ROAS better than cost cap?
Minimum ROAS suits stores with very different order values. Cost cap is simpler when most orders are similar in value.
Written by Shimeez Bok, founder of Growth Alchemy, an ecommerce growth studio in Auckland, New Zealand.
