Soku AIAd Budget Calculator
Two ways to size a budget. Start from the goal — a customer or revenue target — and get the spend required. Then, for Facebook and Instagram, walk that budget down the funnel Meta actually bills on to see whether it buys the conversions you need.
Ad Budget Calculator
To acquire that many customers at this CAC, plan for $5,000 in spend.
Budget = Target new customers × Expected CAC.
Facebook Ads Budget Calculator
Compare this against what one conversion is worth before committing the budget.
Impressions = (Budget ÷ CPM) × 1,000 · Clicks = Impressions × CTR · Conversions = Clicks × conversion rate.
Formula
From a goal: Budget = Target customers × CAC · Budget = Target revenue ÷ Target ROAS || On Meta: Impressions = (Budget ÷ CPM) × 1,000 · Clicks = Impressions × CTR · Conversions = Clicks × CVR
The first pair answers 'how much do I need to spend'; the second answers 'will that spend actually produce the conversions'. Use your own account's CPM, CTR and conversion rate from the last 30 days rather than a published benchmark — Meta CPMs vary by country, audience, placement and season by more than any industry average can capture, and a borrowed CPM is the single biggest source of error in a plan like this.
Worked example
You want 100 new customers and your CAC is $50: budget = 100 × 50 = $5,000. Alternatively, to hit $50,000 in revenue at a 4× ROAS: budget = 50,000 ÷ 4 = $12,500.
Now check that $5,000 on Meta. At a $12 CPM it buys roughly 417,000 impressions. At a 1.2% CTR that is about 5,000 clicks, and at a 3% landing page conversion rate about 150 conversions — an implied CPA near $33. If you needed 200, the budget is short: either spend more, or move CTR or conversion rate, because CPM is set by the auction and is the one number you cannot simply decide.
What this tells you
Budgets set top-down (“we’ll spend $20k because that’s the number”) routinely miss targets. Setting them bottom-up — from a customer or revenue goal and a realistic efficiency assumption — ties spend to outcomes and exposes when a goal is simply unaffordable at your current CAC or ROAS.
That model is fine for a board slide and incomplete for a media plan, because it skips every step where a Facebook campaign actually leaks. Meta charges you for impressions. Whether those impressions become conversions depends on two rates you only partly control — click-through and landing page conversion — and a plan that does not model them cannot tell you whether the target is reachable at all. The second calculator keeps all four numbers visible so you can see which one is carrying the plan.
Benchmarks
How sensitive a Meta plan is to each rate. Same $5,000 budget and $12 CPM, moving one input at a time.
| Change | CTR | Conv. rate | Conversions |
|---|---|---|---|
| Baseline | 1.2% | 3.0% | 150 |
| CTR +25% | 1.5% | 3.0% | 188 |
| Conv. rate +25% | 1.2% | 3.75% | 188 |
| Both +25% | 1.5% | 3.75% | 234 |
Directional ranges only — your targets depend on margins, business model, and stage.
Common mistakes
Assuming CAC or ROAS holds as you scale — efficiency usually degrades with volume.
Setting the budget top-down from a round number instead of from a goal.
Leaving no buffer for the learning phase before campaigns stabilize.
Using a published industry CPM instead of your own. Meta CPM varies enormously by country, audience and season, and a borrowed figure quietly decides the whole plan.
Using the platform's link CTR and your site's conversion rate from different date ranges, which compounds two errors in the same direction.
Forgetting that Meta's daily budget is a pacing target, not a hard daily cap — monthly planning should assume the budget is fully spent.
Treating landing page conversion rate as fixed. It is usually the cheapest of the three rates to improve and the one most often ignored.
When to use it
- Planning monthly or quarterly ad spend from a growth target
- Pressure-testing whether a goal is achievable at your current CAC/ROAS
- Sizing a Facebook or Instagram budget before a launch
- Checking whether a conversion target is achievable at your current rates
- Showing a client or a finance team what a budget cut actually costs in conversions
- Deciding whether to invest in creative (CTR) or the landing page (conversion rate)
FAQ
Which method should I use?
Use the customer-goal method when you have a reliable CAC and a customer target. Use the revenue-goal method when leadership hands you a revenue number and you know the ROAS you can realistically sustain. Then run the Facebook calculator on whichever budget those produce, to check the plan survives contact with Meta's auction.
How much should I spend on Facebook ads per month?
Enough to buy the conversions you need at your current rates, which is what the reverse tab calculates. There is no universal minimum, but there is a practical floor: a campaign needs enough weekly conversions for Meta's optimisation to have signal, so a budget that produces only a handful of conversions a week will perform worse per dollar than the same money concentrated on fewer campaigns. If the plan spreads thin across many ad sets, consolidate before you increase spend.
Should I add buffer to the budget?
Yes — these formulas assume your CAC or ROAS holds as you scale, but efficiency usually degrades with volume. Many teams add 10–20% headroom and revisit after the first weeks of data.
Does Facebook spend exactly my daily budget?
No. Meta treats a daily budget as a pacing target and can spend above or below it on any given day while pacing toward the total over time. For monthly planning, assume the full budget is spent. If you need a hard ceiling, a lifetime or campaign-level budget is the stricter control.
What CPM should I use in the calculator?
Your own, from the last 30 days, for the same countries and placements you plan to run. Pull it from Ads Manager rather than from a benchmark article. If you have no history at all, run a small test to establish a real CPM before committing a full budget — the number is too load-bearing to guess, and it is the one input the auction sets rather than you.
Should I use link CTR or all CTR?
Link CTR, because it counts the clicks that actually reach your site. All-clicks CTR includes reactions, comments, shares and profile taps, so it is a larger number that does not produce landing page sessions. Using it here will overstate clicks and make the plan look achievable when it is not.
Why is my real CPA higher than the calculator's implied CPA?
Usually one of three things. Click-to-session loss, where a meaningful share of clicks never load the page — mobile bounce before load is real and invisible in Ads Manager. Attribution differences between Meta's reported conversions and your own analytics. Or a learning period at launch, when early spend is deliberately exploratory and less efficient than the steady state your rates were measured in.
How do I estimate CAC or ROAS to plug in?
Use your trailing actuals from the same channel and season. If you're launching cold, start with a conservative assumption and let early data correct it.
Is Facebook or Google cheaper for the same conversions?
They are not comparable on CPM, because they sell different intent. Google Search captures demand that already exists and generally converts at a higher rate from a smaller pool; Meta creates demand across a much larger pool at a lower CPM. The honest comparison is CPA on the same conversion event, run in both channels for long enough to clear the learning period. Run this calculator alongside the Google Ads cost calculator on the same conversion target to see the two plans side by side.
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