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Ad math

CPA Calculator

The price of one customer — the number your margin has to beat for paid acquisition to make sense.

CPA = ad spend ÷ conversions. Spend $600 on ads that produce 24 orders and your cost per acquisition is $25 — each $100 of budget buys four customers. CPA is the number to hold against per-order profit: if an order carries $30 of profit before ads, a $25 CPA leaves $5; a $35 CPA loses money on every "successful" conversion. For subscription or repeat-purchase products, compare CPA against first-order profit plus expected repeat margin, not the first order alone. Enter spend and conversions to get both figures.

CPA Calculator — your numbers

Cost per acquisition

$25.00

Conversions per $100

4

Estimate only. Results reflect exactly the numbers you enter — verify against your own accounting before making pricing decisions.

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Worked examples

Healthy DTC acquisition

Ad spend $600.00
Conversions (orders) 24
Cost per acquisition $25.00
Conversions per $100 4

A $25 CPA — profitable for any product clearing more than $25 before ad costs.

Expensive considered purchase

Ad spend $2,000.00
Conversions (orders) 25
Cost per acquisition $80.00
Conversions per $100 1.25

An $80 CPA — workable for high-AOV or subscription products, fatal for a $60 one-off.

Frequently asked questions

What is a good CPA for an online store?

One below your per-order profit before ad spend — there is no universal number. A store netting $45 per order before ads can pay a $30 CPA happily; a store netting $18 cannot. Subscription and repeat-purchase brands can tolerate CPAs above first-order profit because later orders arrive ad-free, but only if retention data actually supports it.

How is CPA different from CAC?

CPA usually counts any conversion (an order, a lead, a signup) from a specific campaign, while customer acquisition cost (CAC) counts new customers only and spreads total marketing cost — including agency fees, creative, and tools — across them. CAC runs meaningfully higher than platform-reported CPA; use CPA to steer campaigns and CAC for business-level decisions.

How do I lower my CPA?

Attack both fractions: CPA = CPC ÷ conversion rate. Cut click costs with better creative and tighter audiences, or lift conversion rate with faster pages, clearer offers, reviews, and a smoother checkout. Conversion-rate work is usually the better lever — a 25% CVR lift cuts CPA 20% across every campaign at once, with no auction fight.

Should I count view-through conversions in CPA?

Be skeptical. View-through conversions credit an ad someone merely saw before buying, and platforms use generous windows to claim them. Including them flatters CPA and can justify budget the ads did not earn. Steer campaigns on click-through CPA, and sanity-check everything against blended math: total spend ÷ total new orders.

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