Cost Per Acquisition (CPA) Calculator
From total ad spend and actions (conversions), compute the cost per action — a measure of ad cost-efficiency.
Input Data
Results
At a glance:CPA = total ad spend / number of actions (any goal: order, sign-up, download). Lower CPA = more efficient. Compare against gross profit per action (e.g. HK$300 profit vs HK$200 CPA = profit). WARNING: CPA ≠ CAC — CPA counts actions (repeatable), CAC counts new customers; numerator should be ad-attributable spend only. Education, not advice.
Formula
CPA = total ad spend / number of actions.
$$CPA = \dfrac{\text{Total Ad Spend}}{\text{Number of Actions}}$$How to Use
- Enter the campaign's total spend.
- Enter the number of actions/conversions.
- View the cost per action.
FAQ
What is the difference between CPA and CAC?
They are related but differ in focus. CPA is cost per action — one customer may contribute many actions. CAC is cost per new customer — the denominator counts only newly acquired customers. Use CPA for per-conversion cost; CAC for the cost to win a customer.
What is an acceptable CPA?
Compare with the value per action. If gross profit per order exceeds CPA, you profit; otherwise you lose. Practically, derive a 'maximum acceptable CPA' from gross profit and use it as a bidding cap, then keep optimising.
How do I lower CPA?
Mainly by raising conversion rate and targeting precision: better creative and audiences, improved landing page and checkout, cutting poor channels/keywords. A higher conversion rate yields more actions for the same budget, lowering CPA. Pair with the conversion-rate calculator.
How do CPA, CPC and CPM differ?
They measure cost at different funnel stages. CPM (cost per mille) = cost per 1,000 impressions (top, reach). CPC = cost per click (middle, traffic). CPA = cost per action (bottom, actual outcome). Typically CPM < CPC < CPA; they convert: CPC = CPM / (clicks per 1,000 impressions), CPA = CPC / conversion rate. CPA is what you judge against gross profit.
Is CPA the same as CAC?
Close but not identical. CPA's 'action' is a broad, customisable goal (download, sign-up, add-to-cart) and its cost is usually only the ad spend. CAC is strictly the cost to acquire a paying customer and often includes wider costs (team salaries, tools, sales). So CAC is usually higher than ad CPA. Use CPA for single-campaign efficiency, CAC for business health (vs LTV, with LTV/CAC ≥ 3 a common rule).
Related Tools
References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.