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Glossary

Ecommerce ad metrics, defined

The numbers that actually decide whether ecommerce advertising makes money, in plain English. Each one is a short definition with the formula and a link to the deeper guide.

ROAS Return on Ad Spend Revenue earned for every dollar of ad spend, written as a multiplier (revenue / ad cost). MER Marketing Efficiency Ratio Total revenue divided by total ad spend across every channel: the whole-business scoreboard. POAS Profit on Ad Spend Gross profit divided by ad spend: ROAS corrected for margin, so it measures money kept, not revenue. Performance Max Performance Max (PMax) Google's goal-based campaign type that serves across every Google surface from one feed-driven campaign. Blended ROAS Blended ROAS Total revenue over total ad spend across all channels: the same calculation as MER. TACoS Total Advertising Cost of Sales Ad spend as a percentage of total revenue: the share of the whole business that goes to ads. ACoS Advertising Cost of Sale Ad spend as a percentage of the revenue it drove: the direct inverse of ROAS. AOV Average Order Value Total revenue divided by number of orders: the average a customer spends per purchase. CPC Cost Per Click The average price you pay for one click on an ad: total cost divided by clicks. CPA Cost Per Acquisition What you pay on average for one conversion: total cost divided by conversions. CTR Click-Through Rate The share of people who click your ad after seeing it: clicks divided by impressions. Quality Score Quality Score Google's 1-to-10 rating of ad relevance, expected click-through rate and landing-page experience. CAC Customer Acquisition Cost The all-in cost to win one new customer across marketing and sales. LTV Customer Lifetime Value The total gross profit a customer brings over the whole relationship, not just the first order. Conversion Rate Conversion Rate The share of visitors or clicks that complete the action you want: conversions divided by sessions or clicks. Impression Share Impression Share The share of the impressions you were eligible for that your ads actually won. Target ROAS Target ROAS (tROAS) A Smart Bidding strategy that bids to hit a return-on-ad-spend goal you set. Smart Bidding Smart Bidding Google's automated, auction-time bidding that optimizes toward a conversion or value goal. Negative Keywords Negative Keywords Terms you exclude so your ads never show for searches that waste budget. Keyword Match Types Keyword Match Types The rules (broad, phrase, exact) that decide which searches trigger your keyword. Engagement Rate Engagement Rate The share of GA4 sessions that were engaged: over 10 seconds, a conversion, or two-plus pageviews. Attribution Model Attribution Model The rule that decides which touchpoints get credit for a conversion.