The key idea
Align account scope, time boundaries, currency and conversion definitions before comparing reports. Calculate combined ROAS from comparable total conversion value and total spend, rather than averaging row-level ratios.
Start with the reporting boundary
Record the accounts, date range and time zone used by each report. Today in an ad account may cover a different interval from today on an operator’s computer. Matching date labels does not necessarily match the underlying period.
A report covering local midnight to the current moment cannot be compared directly with a complete 24-hour day, even if the headings look alike. Align the boundaries and identify any period that is still in progress.
- Are the account list and reporting level identical?
- Do the start time, end time and time zone match?
- Does either report have extra filters?
Identify what conversion value means
Conversion value depends on the conversion events selected and the values assigned to them. Platform-attributed conversion value and order totals from a business system should not be treated as the same field simply because both use a currency.
Document the event, attribution scope, currency and treatment of adjustments such as refunds. The purpose is to establish a definition someone else can reproduce. The official Google Ads reference below explains the basic role of conversion values.
Recalculate the combined ratio
ROAS is conversion value divided by advertising spend. To aggregate comparable rows, sum the values and costs separately before dividing. Amounts in different currencies also need an explicit conversion policy before they can be added.
Consider a calculation example, not a performance benchmark: group A spends 100 and records value of 300, giving ROAS of 3. Group B spends 900 and records value of 900, giving ROAS of 1. With the same currency and reporting definition, combined ROAS is 1200 / 1000 = 1.2. Averaging 3 and 1 would incorrectly produce 2.
The ratio is not a profit margin. Product costs, refunds and other operating expenses belong in a separate profitability analysis.
Keep missing values distinct from zero
Zero is an observed value under a defined scope. Missing means no usable result is available. Incomplete access, pending synchronization or an inapplicable field should retain their unavailable status instead of becoming zero in a report.
When a total looks wrong, preserve the filters, refresh time and list of uncovered accounts. Check coverage before interpreting the number. When spend is zero, do not manufacture a sortable ROAS by forcing a division.
- Record when each report was last refreshed.
- Identify unauthorized, unsynchronized or inapplicable items.
- Keep the underlying spend and conversion values available for recalculation.
Frequently asked questions
Why not average the ROAS of each account?
Accounts have different spend weights. For comparable data in the same currency, divide total conversion value by total spend.
Can missing data temporarily be recorded as zero?
Keep unavailable data distinct from an observed zero. Show the missing coverage or reason, then reconcile again when the data becomes available.