Google Keyword Planner Search Volumes Are Mostly Overestimates

Executive overview

Google Keyword Planner is widely trusted because its data comes from Google — but that trust is largely misplaced. An Ahrefs study of 72,635 keywords found that Keyword Planner dramatically overestimates search volume more than half the time. The root cause is keyword grouping: Planner bundles semantically different queries into a single bucket and sums their volumes, inflating numbers for any individual term. Third-party tools that report distinct, ungrouped volumes are measurably more accurate. For content planning, traffic potential is a more reliable signal than raw search volume.

What the study measured

• 72,635 random keywords with 1,000–10,000 monthly searches
• Compared Keyword Planner estimates against Google Search Console impressions for June 2021
• Pages had to rank in the top 10 for the keyword to ensure impressions reflected true search demand
• "Roughly accurate" defined as within 50% of Search Console impression count — a generous threshold

Key findings

• Keyword Planner overestimated search volume 91% of the time vs. Search Console impressions
• Drastically overestimated (more than 2x impressions): 54% of keywords
• Roughly accurate (within 50%): 45% of keywords
• Drastically underestimated: only 0.5% of keywords
• 14.8% of keywords were overestimated by 4x or more

Why Keyword Planner overestimates

• Keyword grouping merges queries with similar or overlapping meanings and sums their volumes
• Benign groupings: misspellings of the same brand (e.g. "Ahrefs" variants) — minor inflation
• Harmful groupings: "Bank of America" (navigational) grouped with "American Banks" / "Banks in America" (informational) — all shown with 16M+ monthly searches despite vastly different intent and true demand
• Google Trends confirms the grouped queries have far lower individual volume than Planner reports
• Local-intent queries drive the worst overestimates (4x+): a query like "golf courses" returns entirely different SERPs by city, so country-wide Planner volumes are meaningless for most sites

How Ahrefs compares

• Drastically underestimated: 1.84% vs. Planner's 0.5%
• Roughly accurate: 60.68% vs. Planner's 45.22%
• Drastically overestimated: 37.48% vs. Planner's 54.28%
• Improvement attributed to ungrouping keyword clusters and reporting distinct volumes per query

Practical takeaways

• Keyword Planner is better than guessing, but not reliable for individual keyword decisions
• Use a third-party tool that ungroups keywords for more accurate volume data
• Prioritize traffic potential over search volume — it estimates total traffic from ranking #1, accounting for the fact that pages rank for many keywords with varying click-through rates
• Be especially sceptical of Planner volumes for local-intent queries and broad informational terms