How to use the ad budget calculator
Enter how many sales you want and how many days the period lasts.
Add your average order value and the conversion rate from click to purchase.
Choose how you know your traffic cost: a CPC, or a CPM together with a CTR.
Add your gross margin to check whether the plan is profitable at those numbers.
The ad budget formula
- Clicks needed=target sales ÷ conversion rate
- Budget=clicks needed × CPC
- Budget=clicks needed ÷ CTR ÷ 1,000 × CPM
- Daily spend=budget ÷ days
- Implied ROAS=target sales × AOV ÷ budget
- Conversion rate
- Purchases divided by link clicks. Use the rate for paid social traffic, not the site-wide average.
- CPC, CPM and CTR
- From your Ads Manager history for the same country and objective. The second budget line is used when you plan with CPM and CTR.
- AOV
- Average order value, excluding tax.
Worked example
Planning 300 sales in a month
- Goal: 300 sales in 30 days. AOV 60, conversion rate 3%, CPC 0.80.
- Clicks needed = 300 ÷ 0.03 = 10,000.
- Budget = 10,000 × 0.80 = 8,000, or about 267 a day.
- Revenue = 300 × 60 = 18,000, so implied ROAS = 18,000 ÷ 8,000 = 2.25x.
- With a 50% margin, break-even ROAS is 2.0x.
Assumptions make or break the plan
The output is only as good as the conversion rate and CPC you feed in. Use figures from paid traffic on the same store and country, not site-wide averages that include returning visitors and email traffic, which usually convert far better.
Run the calculator three times: realistic, pessimistic and optimistic. If the pessimistic case loses money, start with a smaller test budget and scale only once real numbers confirm the plan.
Costs rise as you scale
Funnel numbers are not linear. As daily spend grows, the platform has to reach people who are less likely to buy, so CPC and CPA tend to climb. A plan that works at 100 a day may not work at 1,000 a day.
- Increase budgets in steps and re-measure CPA at each level.
- Keep a share of spend for creative testing so you have new winners ready when old ones fatigue.
- Revisit the plan monthly with your actual CPC and conversion rate.
How much budget to test with
A common approach is to give each ad set enough budget to produce a meaningful number of conversions in a week. Meta's guidance is about 50 optimization events per ad set per week to exit the learning phase; at a 30 CPA that is roughly 1,500 a week for one ad set.
If that is out of reach, consolidate into fewer ad sets or optimize for a higher-volume event such as add to cart while you gather data, and judge the result on purchases.
Questions and answers
How much should I spend on Facebook ads?+
Enough to reach your sales goal at a CPA you can afford. Work out the clicks your goal needs from your conversion rate, multiply by your CPC, and check the result against your margin. This calculator does exactly that.
How do I calculate daily ad spend?+
Divide the budget for the period by the number of days. A 9,000 monthly budget over 30 days is 300 a day.
What conversion rate should I assume?+
Your own paid social conversion rate is the best input. Many ecommerce stores see somewhere between 1% and 4% from cold paid social traffic, but it depends heavily on price, offer and landing page. Without data, test small before committing a full budget.
Should I plan with CPC or CPM?+
Use whichever you trust more. CPC is simpler. CPM with CTR is useful when you plan new creative, because you can see how much a better CTR would reduce the budget you need.
Does the budget include agency fees or creative costs?+
No. It is media spend only. Add creative production, tools and agency fees separately when you plan the total marketing budget.
Why is my real ROAS lower than the plan?+
Usually because conversion rate or CPC worsened as spend increased, or because the plan used a site-wide conversion rate. Update the inputs with actual results after the first week.