Facebook Ads Budget Calculator
Work out the total Facebook Ads budget needed to hit a specific conversion target given your landing page conversion rate, expected CTR, CPM, and campaign duration. Use it before launching any paid campaign to avoid under- or over-spending.
About this calculator
To generate a target number of conversions on Facebook, you must work backwards through the funnel from conversions to impressions, then price those impressions using CPM. The formula is: Budget = (targetConversions / (conversionRate/100) / (ctr/100) × (cpm/1000)) × (campaignDuration/30). First, targetConversions / (conversionRate/100) gives the number of clicks needed. Dividing by (ctr/100) converts clicks into required impressions. Multiplying by (cpm/1000) prices those impressions in dollars, yielding a monthly budget. Finally, multiplying by (campaignDuration/30) scales the monthly figure to the actual campaign length. Every variable is under partial marketer control: improving CTR via better creative reduces required impressions; improving landing-page conversion rate reduces required clicks; negotiating lower CPM via audience targeting reduces cost per impression.
How to use
Goal: 200 conversions. Conversion rate: 5%. Expected CTR: 2%. CPM: $10. Campaign duration: 14 days. Step 1: Clicks needed = 200 / 0.05 = 4,000. Step 2: Impressions needed = 4,000 / 0.02 = 200,000. Step 3: Monthly cost = 200,000 × ($10/1,000) = $2,000. Step 4: Scale to 14 days = $2,000 × (14/30) = $933. Enter these five values and the calculator returns a required budget of approximately $933.
Frequently asked questions
How do I estimate my Facebook Ads CTR before launching a campaign?
If you have run Facebook campaigns before, use your historical average CTR from Ads Manager as a starting point — most advertisers see 0.5–2% for feed ads and 0.5–1% for Audience Network placements. If you are launching for the first time, industry benchmarks by vertical from WordStream suggest e-commerce averages around 0.7–1.2%, while finance and insurance can reach 0.5–0.8%. It is safer to be conservative (use a lower CTR) when budgeting so you do not underfund the campaign. After the first 3–5 days of a live campaign, replace the estimate with your actual CTR and recalculate to adjust spend.
What CPM should I use when planning a Facebook Ads budget?
CPM on Facebook varies widely by audience, placement, industry, and time of year, ranging from $5 for broad cold audiences in off-peak periods to $30+ for highly targeted retargeting audiences in Q4. Your Facebook Ads Manager will show historical CPMs if you have run ads before; otherwise, use $10–$15 as a conservative planning estimate for most B2C campaigns. CPM spikes during Black Friday, Christmas, and election periods, so add a 20–40% buffer if your campaign runs during those windows. Using a higher CPM estimate when planning ensures you have sufficient budget even if auction prices rise unexpectedly.
Why does campaign duration affect the total Facebook Ads budget needed?
Facebook's delivery algorithm optimises spend over time, but the total budget needed is fundamentally tied to how many impressions you must purchase to hit your conversion goal — and those impressions cost money regardless of the time frame. The duration multiplier (campaignDuration/30) simply prorates the monthly cost to your actual campaign window. A 14-day campaign needs roughly half the budget of a 30-day campaign for the same conversion target, assuming CPM and rates stay constant. In practice, shorter campaigns sometimes have higher effective CPMs because Facebook's algorithm has less time to find efficient delivery windows, so the calculated budget should be treated as a floor rather than a ceiling.