SEO Metrics Handbook — The Complete Guide
If you're making decisions based on SEO metrics, those metrics need to be correct. This handbook covers every metric that matters — with formulas, visual examples, and the common mistakes that lead to bad SEO decisions.
If your CTR formula divides by zero or your position average isn't weighted, your entire SEO strategy is based on wrong data.
Most SEO tools get metric calculations subtly wrong — simple position averages, naive CTR aggregation, division-by-zero gaps. These small errors compound into misleading dashboards that lead to bad decisions. This guide shows you the correct formulas and why they matter.
The 4 Core GSC Metrics
Clicks
Volume metricThe total number of times users clicked through to your website from Google Search results. This is the most direct measure of organic search traffic. Clicks are the ultimate outcome metric — everything else (impressions, CTR, position) is a leading indicator.
Aggregation
Total sum of all clicks across selected pages and queries.
Impressions
Visibility metricHow many times your pages appeared in Google Search results. An impression is counted when Google shows your URL in results, regardless of whether the user actually sees it (they may not scroll that far). High impressions with low clicks means you're visible but not compelling.
Aggregation
Total sum of all impressions across selected pages and queries.
CTR (Click-Through Rate)
Efficiency metricThe percentage of impressions that result in clicks. CTR is the best indicator of how compelling your search listing is. It combines the effect of your ranking position, title tag, meta description, rich snippets, and brand recognition.
Formula
CTR = clicks ÷ impressions
Guard: if impressions = 0, CTR = 0
Correct aggregation
Total clicks divided by total impressions — not the average of individual CTR values.
Simple averaging produces misleading results. SEOInputs handles this automatically.
Average Position
Ranking metricYour average ranking position in search results. Position 1 = top of page. Lower is better. This is the most misunderstood metric because it must be weighted by impressions. A simple average treats a query with 1 impression the same as one with 100,000 — which is statistically meaningless.
Correct calculation
Impression-weighted average — high-traffic queries count more than low-traffic ones.
A simple average treats all queries equally, which is statistically meaningless. SEOInputs uses the correct weighted method.
Display convention
Position decrease = moving up in rankings = positive. Show green arrows when position decreases (improves). This is inverted from click/impression deltas.
Content Intelligence Metrics
Metrics derived from GSC data that power content strategy decisions.
Content Decay Rate
Measures how fast a page is losing organic traffic. Calculated using rolling time windows comparing the current period to the previous period. This catches gradual declines that aren't visible in day-to-day data.
Growing
Traffic up
Stable
Minimal change
Declining
Traffic dropping
Crashed
Severe loss
Opportunity Score
Quantifies the untapped potential of keywords at striking distance (positions 4–15). High-impression keywords with low CTR have the most room for improvement.
Only non-branded queries. Position weight decreases as position improves (less room to gain).
Cannibalization Severity
When multiple pages compete for the same query, Google's algorithm oscillates between them. Severity is calculated from position variance (how much ranking fluctuates) weighted by impression volume (how important the query is).
Minimum threshold: queries with < 100 impressions/month excluded. Branded queries with homepage + subpage are normal, not cannibalization.
Delta Percentage
The percentage change between two periods. Used throughout SEOInputs for comparing KPIs, page performance, and keyword trends.
Guard: if previous = 0 and current > 0, delta = +100%. If both are 0, delta = 0%.
Common Metric Mistakes
Even experienced SEOs get tripped up by these calculation errors.
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