What key metrics should I regularly monitor to detect poor ad performance?

The Monday written summary

Every account I run gets a Monday morning written summary. Four numbers, one paragraph, sent before anything else opens. The point is not the document. It is reading the same numbers the same way every seven days, so a drift registers as a drift instead of a month-end surprise. Each number below names its report.

The four weekly numbers

CPA trend

Cost per acquisition at the account level, then for the top three campaigns by spend, on a rolling seven-day window against the prior seven days and the trailing twenty-eight. One week in isolation is noise; the trend across three windows is signal. Concern threshold: a top-three campaign twenty percent above its trailing twenty-eight-day baseline. First move: that campaign’s search terms report, before bids.

Spend pacing

Month-to-date spend divided by days elapsed, multiplied by days in the month, against budget. Pacing to a hundred and forty percent of budget in the first ten days means a bid strategy off its leash. Pacing to fifty percent means starving the auction. Concern threshold: fifteen percent above or below target by the second Monday. First move: change history for the prior fourteen days.

Zero-conversion spend share

The report: campaigns or ad groups view, cost descending, conversions filtered to zero, last thirty days. Total every ad group that spent over a hundred dollars and produced nothing, divided by total account spend. Under ten percent is healthy on a mature offer; twenty-five to forty means drift. Concern threshold: twenty-five percent. The cause is usually three or four ad groups the bid strategy will not defund because its conversion signal arrives too rarely to retrain the model.

Impression share, split by budget and rank

The report: campaigns view with Search Lost IS (budget) and Search Lost IS (rank) added, week over week. Lost-to-budget means the campaign hits daily cap and Google would spend more. Lost-to-rank means it cannot win the auction at the bid and Quality Score it has. The two dictate completely different fixes: ten percent lost to budget on a healthy conversion rate leaves revenue on the table, thirty percent lost to rank bleeds click cost on the impressions you win. Concern threshold: impression share down ten points in seven days, or lost-to-rank up five points in a week.

Search campaigns: seven numbers behind three reports

The default view rewards more match types and more spend. These seven sit further in.

Search-term irrelevance rate

The report: search terms, last ninety days, cost descending. Tag the top two hundred queries relevant or irrelevant, divide irrelevant cost by total cost. Under ten percent is healthy on tight match types; a Performance Max or broad-match heavy account often sits between thirty and sixty. Concern threshold: fifteen percent of spend on queries you would not have bid on by hand, and above twenty-five percent treat it as structural. The fix is rarely a longer negative list. It is tighter match types, audience signals on Performance Max, and a decision about where broad match operates.

Top-spend keyword performance

The top ten keywords by spend carry sixty to eighty percent of Search cost. Read them weekly: spend, clicks, conversions, conversion rate, CPA. One going off the rails masks a healthy account average for two or three weeks, so reading the ten weekly catches it on day seven instead of day twenty-one. Concern threshold: a seven-day conversion rate below half the trailing ninety-day rate. First move: the search terms it triggered, and its match type.

Quality Score on top-spend keywords

The report: keywords view with Quality Score, Landing Page Experience, Ad Relevance, and Expected CTR added, cost descending. A score below 5 on a keyword taking more than a few percent of campaign spend is a tax: Google charges fifteen to forty percent more per click than it charges competitors with strong scores. Three below 5 in the top ten by spend calls for a landing-page and ad-copy rebuild. Two is a warning. One is noise.

Monthly, widen to the top fifty and bucket them seven-or-higher, four-to-six, three-or-lower. Twenty percent slipping into the bottom bucket means CPCs rise account-wide whatever the bid strategy says. Concern threshold: a five-point swing toward the lower buckets in one month. The Wasted Spend Calculator covers the uplift math.

Click-through rate on exact-match keywords

The report: keywords view filtered to match type equals exact, impressions descending. Median ecommerce CTR on exact match sits between 4 and 8 percent branded and 2 and 4 percent non-branded, and a service business with strong intent queries should clear 5 percent non-branded. Under 1 percent with real impression volume means the keyword is matching queries it no longer represents, or the ad misses the intent.

Conversion rate by match type

The report: dimensions or segment view, segmented by match type at ad group level. Exact should convert highest, phrase lower, broad meaningfully lower than phrase. When the order inverts the data is lying, almost always from a tracking de-duplication failure or a branded query slipping into broad. A broad-match rate that doubles the exact rate on the same keyword root means broad is intercepting branded traffic you already had. The Tracking Stack reference covers the de-duplication contract.

Impression share by audience segment

The report: audiences view inside a campaign, impression share segmented by audience. Customer Match lists fed from email and SMS should clock the highest impression share and conversion rate, because logged-in past purchasers searching category terms are the cheapest conversions in the account. If they sit low while cold audiences absorb the spend, layer the audience as a bid modifier and raise the floor. Same budget, different result inside two weeks.

Top impression rate against rising CPC

The report: search campaigns view with Top Impression Rate, Absolute Top Impression Rate, and Average CPC added, last thirty days against the previous thirty. When top impression rate falls while CPC rises, you are paying more per click for worse placement. Concern threshold: a ten-percentage-point drop paired with a fifteen-percent rise in CPC inside thirty days. You are outbid on rank, not on budget, and more bid will not recover the position.

Display and Performance Max: six numbers Google buries

Search has the search-terms report, where a bad query carries a name and a cost. Display has no equivalent. Google files placements under Insights, and Performance Max scrubs most of it into a “Placements where your ads appeared” download with no spend column. These placements absorb thirty to seventy percent of the budget in most solo-founder accounts, and almost nobody audits them.

Placement category share

The report: Insights or Where ads showed, sorted by cost, mobile-app placements broken out. The top fifty placements should produce more than seventy percent of meaningful engagement. Concern threshold: the top fifty accounting for less than thirty percent of total spend. A thousand placements taking ten dollars each is the canonical Performance Max display leak. First move: export placements, sort by cost, exclude the long tail below a minimum click threshold. Thirty minutes in the account-level exclusion list at the MCC.

Viewability rate

The report: campaigns view with Active View Viewable Impressions divided by total impressions, or the Insights tab on Performance Max. Google’s Active View documentation defines a viewable display impression as fifty percent of the ad on screen for one second, and a viewable video impression as fifty percent on screen while playing for two seconds. Under sixty percent means more than four in ten measurable impressions never crossed that line. Below-the-fold and “below 300x250 mobile sticky” exclusions alone often lift it ten points inside a week.

Mobile-app placement spend

The report: placement type filter set to mobile-app in the Where ads showed view. The highest-friction inventory in the system: children’s games and lock-screen tap traps. Click-through rates look exceptional, conversion rates collapse, session duration sits under three seconds because most clicks were accidental. Concern threshold: mobile-app spend above five percent of display budget. Exclude mobileappcategory::69500 (Games), then the Display Network mobile-app exclusion at account level. Performance Max needs the same exclusion through the Account-Level Negative Placements list at the MCC, released quietly in 2023 and rarely opened.

View-through to click ratio

The report: conversions segmented by attribution type, view-through against click-through. A view-through conversion fires when someone saw the ad and converted later without clicking. Useful as a directional signal, dangerous as a KPI. Above 100 to 1 the platform is claiming almost every conversion off an impression that may have been one pixel tall on a content farm. Cap the window at thirty days and keep those conversions out of any ROAS used to set bids; the Google default of ninety days hides the leak. Four-times return on clicks and twelve-times on view-through is a campaign that needs the click number.

Audience overlap

The report: audience insights at campaign level with overlap percentage against Customer Match and remarketing lists. On Meta, the audience overlap tool. A prospecting campaign that overlaps the remarketing list is buying impressions on people who already converted, and retargeting would have reached them at a lower CPM. Performance Max does this constantly, firing at warm audiences because they convert faster and make the asset group look efficient. Meta fails differently: two prospecting ad sets on overlapping audiences bid against each other while both report as functional. Concern threshold: thirty percent overlap against remarketing on Display, twenty percent between two Meta prospecting ad sets. First move: consolidate or rebuild into distinct buckets.

Engagement and session duration on paid traffic

The report: GA4 traffic-acquisition view, source filtered to paid, engaged sessions and average session duration against total sessions. GA4 counts a session as engaged if it lasts ten seconds or longer, fires a conversion event, or includes two or more pageviews. Healthy paid traffic runs forty to sixty percent non-engaged; seventy percent or more means broad-match queries on irrelevant pages, app placements, or a page taking over three seconds to render on mobile. Segment to display and read session duration: fifteen seconds is the floor, and below five seconds accidental clicks dominate.

The monthly revenue check

Four numbers on the first Monday, all asking whether the spend turned into money.

Blended ROAS against Shopify

Compare platform-reported ROAS against the revenue Shopify attributes to paid traffic: Shopify Analytics, Reports, Sales by traffic source, same range. The gap is the metric. Inside ten percent says the tracking stack is honest. Above twenty-five percent says the platform is claiming revenue Shopify cannot see, and no bid change fixes a tracking problem. Sales by referrer adds the second layer, showing referring URLs, and catches a click parameter stripped at checkout. Concern threshold: Shopify reporting thirty percent less paid revenue than Google Ads. First move: server-side conversions, a GA4 enhanced measurement audit, and a recheck of the consent banner blocking the pixel on a quarter of EU sessions.

New-customer ROAS

Total ROAS hides repeat purchases. A returning-customer order through a paid click is a margin loss most months, because that customer would have bought through email or direct. New-customer ROAS, isolated through Shopify customer reports or the platform’s new-customer acquisition column, says whether paid pays for itself. A blended ROAS of three-point-five against a new-customer ROAS of one-point-two means paid is subsidising the existing-customer base rather than building one. Concern threshold: below contribution-margin breakeven for two months.

Cost per conversion against target CPA

The report: campaigns view with Cost per Conversion and Target CPA visible, segmented by week for the last ninety days. A week inside twenty percent of target is on plan. Fifty percent or more above target for three consecutive weeks is structural. Both platforms let actual CPA roam above target on the belief a future conversion is likely, and three weeks of being wrong calls for a manual reset, not more learning time. The fix is a tighter conversion definition, a lower target, or a pause on the worst ad group.

Conversion volume against rising spend

The report: campaigns view with Cost and Conversions plotted as a time series, last six months, weekly. In a healthy account the lines move together; in a decaying one spend climbs while conversions flatten. Concern threshold: cost per conversion climbing more than thirty percent over a rolling sixty-day window while spend is flat or rising. The cause is audience saturation, creative fatigue past recovery, or a tracking change that broke attribution. The target-CPA calculator says whether the new number still clears margin.

The four reports that explain the numbers

Metrics say something moved. These four say why, in this order.

Auction insights, campaign and ad group level, top three spenders. Watch for impression share lost to budget above twenty percent on campaigns that used to clear inventory, and a new competitor in the top three with a high overlap rate. Concern threshold: outranking share dropping fifteen points month over month. Fix: bid cap review, ad rank diagnosis, and a check on a competitor’s new price promotion.

Change history, the most under-used report in Google Ads. Filter the break period by change type: budget, bid strategy, Performance Max assets, conversion goals. Half the accounts I audit have one change that explains the entire drop, usually a bid strategy switched to maximize conversions on thin conversion data. Concern threshold: any bid strategy change inside the underperformance window. Fix: revert it and run the original strategy for a full conversion cycle.

The Performance Max asset report, next to the placement report. Performance Max accounts for most wasted-spend complaints I see in 2026, and the asset report often shows the algorithm fixated on one headline or image that produces clicks and no orders. Concern threshold: over thirty percent of Performance Max spend on Display placements with sub-one-percent conversion rates. Fix: placement exclusions and asset group splits by intent.

GA4 landing pages: Pages and Screens, Session source / medium secondary, filtered to google / cpc, read against engagement rate. A page taking fifteen percent of paid traffic at forty-percent engagement and a two-percent conversion rate is the leak, not the keyword that sent the click. Concern threshold: a top-five paid landing page under fifty percent engagement, or under one percent of site-average conversion rate. Fix: rebuild it or reroute the traffic.

The cadence is the product

On a roofing client I monitor weekly, the dashboard showed twenty-one thousand clicks at a dime each across the trailing ninety days. Top-decile by every surface metric. The cadence caught what the dashboard did not: the campaigns were lead-form objectives where every form open registered as a click, and the form-completion rate against those opens was barely under five percent. The founder would have kept scaling spend against the leak. The metric that matters is rarely the metric the platform highlights.

If I open one number first it is the zero-conversion spend share, the fastest read on whether the problem is tuning or structure. On Search that job belongs to search-term irrelevance, which distorts every metric downstream. On Display it is placement category share: the long tail explains the collapsed viewability, the mobile-app spend, and the three-second sessions. Two of the six search numbers out of band usually costs fifteen to thirty percent of budget; three of the six display numbers usually costs twenty to fifty percent of that line item. The numbers matter less than reading them on the same day, in the same order, every week.

Run the free 25-page setup audit for the diagnostic written out, use the Wasted Spend Calculator to size the leak in dollars, or read the wasted-ad-spend library. The services overview walks the structural fix. Founders who want me running this cadence live can send the account read-only through the contact form.