Formulas used by this calculator
- ROAS = ad-attributed revenue ÷ ad spend
- ACOS (%) = ad spend ÷ ad-attributed revenue × 100
- When both inputs are positive: ACOS (%) = 100 ÷ ROAS
Worked example
Illustrative ad spend: $1,000. Ad-attributed revenue: $4,000.
ROAS = 4,000 ÷ 1,000 = 4×. Each unit of media spend has four units of attributed revenue.
ACOS = 1,000 ÷ 4,000 × 100 = 25%. Media spend equals one quarter of attributed revenue.
Choose numbers that belong together
Start with one campaign or account scope and a defined reporting period. Keep the currency and attribution settings consistent. Do not compare account-wide spend with revenue from only one campaign, or combine figures copied from reports that use different conversion windows.
Amazon describes ACOS as advertising spend divided by attributed sales, with ROAS expressing the inverse relationship. Those definitions explain the arithmetic; they do not determine a profitable target for your business. Amazon Ads: ACOS and ROAS definitions.
Decide whether the revenue figure is gross, net of discounts, or adjusted for refunds. Write that definition beside the result in your own reporting process. A change in revenue treatment can move ROAS even when customer behavior has not changed.
Interpret the ratio before changing a budget
A 4× ROAS does not mean a 300% profit. The calculation excludes product costs, fulfillment, payment fees, labor, software, and other expenses. Two products can report the same ROAS while leaving very different contribution after advertising.
The result also reflects the reporting system's attribution rules. It does not prove that every credited sale was caused by advertising, nor that the next increment of spend will produce the same ratio. Use an appropriate experiment when the decision requires an estimate of incremental impact.
Recent reporting periods can be incomplete. A customer may convert after the initial ad interaction, and an imported outcome may arrive later still. Compare periods with similar maturity before treating a lower recent ROAS as evidence that the campaign has deteriorated.
Use the worksheet for a consistent review
Download the inputs, definitions, and results as a CSV after calculating. The worksheet makes the arithmetic portable; add your report dates, account scope, and attribution settings before sharing it with someone making a budget decision.
To combine multiple campaigns, add their compatible spend and revenue totals first, then calculate the overall ratio. A simple average of campaign ROAS values gives a small campaign the same weight as a large one and can misrepresent the combined result.
Common questions
What happens when revenue or spend is zero?
With spend but no attributed revenue, ROAS is zero and ACOS is undefined. With revenue but no spend, ACOS is zero and ROAS is undefined. If both are zero, both ratios are undefined. The calculator never presents a zero-denominator result as a usable infinity.
Is there one good ROAS or ACOS target?
No single target fits every margin, cost structure, business objective, and attribution setup. Use the break-even calculator to model your own contribution economics, then assess measurement quality and the effect of additional spend.
Does changing currency convert the amounts?
No. The currency selector changes display labels only. Enter spend and revenue in the same currency after performing any required reconciliation separately.