CPA Calculator
CheckedUse this CPA calculator to find your cost per acquisition and the highest CPA your margin can afford before every order loses money. Free, no sign-up, and the result updates as you type.
Enter your numbers
A CPA is only high or low relative to what one customer is worth, and the worth is gross profit, not order value. A $50 CPA on a $120 order sounds comfortable until the 38% margin on that order turns out to be $45.60, at which point every acquisition loses $4.40 and the campaign scales the loss. This calculator reports the CPA you are paying and the maximum CPA your margin can carry, so the gap between them is a dollar figure rather than a feeling.
How it's calculated
CPA = ad spend ÷ conversions Max CPA = average order value × gross margin
LaTeX source
\text{CPA} = \frac{S}{C} \qquad \text{Max CPA} = \text{AOV} \times m Worked examples
A campaign with room to bid harder
$30.00 CPA against a $42.75 ceiling
$2,400 over 80 conversions is a $30.00 CPA. A $95 order at a 45% gross margin yields $42.75 of gross profit, so each acquisition nets $12.75 and there is 29.8% headroom before break-even. That headroom is the case for raising bids: volume bought at anything under $42.75 still adds profit, even as CPA rises.
The numbers used
- Ad spend
- 2400
- Conversions
- 80
- Average order value
- 95
- Gross margin
- 45
A campaign already over the line
$50.00 CPA against a $45.60 ceiling
$5,200 over 104 conversions is a $50.00 CPA. At a 38% margin a $120 order carries $45.60 of gross profit, so the campaign is $4.40 underwater per acquisition and 9.6% past its ceiling. Across 104 orders that is $458 of loss, hidden inside a dashboard reporting a perfectly normal 2.40× ROAS.
The numbers used
- Ad spend
- 5200
- Conversions
- 104
- Average order value
- 120
- Gross margin
- 38
Questions sellers ask
How do you calculate CPA?
Divide total ad spend by the number of conversions it produced. $2,400 of spend and 80 orders is a $30.00 CPA. Keep the numerator and denominator on the same window and the same attribution setting, because a 7-day click window and a 1-day window will not report the same conversion count for identical spend. Then compare the result against gross profit per order, not order value.
What calculator can you use on CPA?
For cost per acquisition, any tool that divides spend by conversions will do, including this one — the value is in the max-CPA ceiling it computes alongside. If the question is about the CPA accounting exam, the AICPA supplies an on-screen calculator in the testing software and separately permits the TI BA II Plus and HP 12C in some sections. Those are unrelated to advertising CPA.
What calculator is recommended for the CPA exam?
The exam software includes a built-in on-screen calculator and a spreadsheet tool, and most candidates use those rather than bringing hardware. Where a handheld is permitted, the TI BA II Plus is the common choice for time-value-of-money work. This page is about the advertising metric of the same name — cost per acquisition — which is a campaign number, not an accounting one.
What is the CPA equation?
CPA = total ad spend ÷ total conversions. Two useful rearrangements follow from it: conversions = spend ÷ CPA, which sizes a budget against a volume goal, and max CPA = average order value × gross margin, which sets the ceiling. You can also reach CPA from click data as CPC ÷ conversion rate, so a $1.25 CPC at a 3.2% conversion rate implies a $39.06 CPA.
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