Max CPA calculator

Worked example

Order value 1,200 before tax; variable cost per order 720 (product 480, shipping 120, payment fees 36, packaging 24, returns 60); keep 10% of the order as profit:

Item	Working	Result
Break-even CPA	1,200 − 720	480
Profit kept	1,200 × 10%	120
Target CPA	480 − 120	360
Target ROAS	1,200 ÷ 360	3.33
Affordable CPC (2% conversion rate)	360 × 2%	7.2

The last row works upstream: a 2% conversion rate means 1 order per 50 clicks, so each click may cost at most 360 ÷ 50 = 7.2.

Using it to decide when to stop

Max CPA gives you two lines:

• Break-even CPA (480) is the stop line. An ad set whose CPA stays above it loses money on every extra order.
• Target CPA (360) is the bar for more budget. Raising spend only makes sense below it, with enough purchases to trust the number.

Small budgets often cannot wait for purchases. Use the upstream limits to decide earlier: if spend has passed break-even CPA with no purchase yet, or clicks keep costing more than the affordable CPC, you do not need to wait for a full sample to stop.

Common mistakes

• Setting target CPA at break-even. Ads that exactly break even pay nothing towards fixed costs and leave no profit. The target has to sit below break-even.
• Keeping too much profit. If the profit you want to keep exceeds the contribution per order, there is no ad budget at all and the calculator shows "—". The fix is price or cost, not CPA.
• Looking only at the average. An account averaging 360 can be one ad set at 200 and another at 600. Compare set by set; the 600 one is already past the stop line.
• Reading a bid target as a guarantee. Google Ads target CPA bidding lets some conversions cost more and some less, aiming for the average. Watch the actual CPA yourself.

FAQ

How do you calculate CPA?

CPA = ad spend ÷ conversions. Spend 9,000 for 25 orders and CPA is 360.

What is the difference between max CPA and target CPA?

Max CPA (break-even CPA) is the line past which you lose money. Target CPA takes off the profit you want to keep, so it always sits below it.

How does this work without an order value, for leads?

Replace order value with the gross profit one lead brings on average. If 1 in 10 leads becomes a customer worth 6,000 in gross profit, each lead is worth 600, and the break-even CPA for a lead is 600.