Align the inputs first
Use the same reporting period, currency and attribution window for each channel. Name the report and record the period clearly. Enter zero only when the metric is actually zero; blank values are not silently assumed to be zero. Fractional attributed conversions are supported.
Calculate from totals
CTR is clicks divided by impressions. CPC, CPM and CPA divide spend by clicks, thousands of impressions and conversions respectively. ROAS divides attributed revenue by spend. The combined row uses sums of the underlying values, which avoids misleading simple averages of channel ratios.
Add the interpretation
Explain the result, supporting evidence and next actions in your own notes. The tool does not invent a reason for a performance change. Platform conversion totals can overlap and do not represent deduplicated customers. Export the report and review attribution before sharing with a client.