Operator glossary
Keyword coverage
The share of a category's measured search demand that your indexed words can actually reach — the metric that turns a character limit into a business number.
Coverage asks a different question than a keyword count does: not how many phrases you target, but what share of real demand those phrases represent. Compute it by sorting a category's phrases by search volume, then charging each phrase only for the words it introduces that you have not already indexed. Coverage rises fast at first and then flattens hard, because later phrases are both smaller and share most of their words with earlier ones.
This is the right frame for every character limit Amazon imposes. It tells you whether a field is load-bearing or decorative for your specific category: where one head term dominates, a title alone already covers most demand and extra fields are refinement; where demand is fragmented across modifiers, the same characters buy far more. Treat the resulting figures as ceilings — the arithmetic assumes unique keyword words with no brand and no grammar, while a real title spends 20-30 characters before it earns its first optional keyword.
The numbers
- Measured (Helium 10, Aug 2026, US): 75 title characters cover 70.9% of 'air fryer' demand, 76.5% of 'yoga mat', and 55.2% of 'office chair'.
- Adding the 125 Item Highlights characters lifts those to 82.2%, 87.0% and 71.0% — a gain of 10.5 to 15.8 percentage points, largest where the head term is weakest.
- Covering every measured phrase in those categories would need 739, 542 and 1,015 unique-word characters — three to five times the 200 characters the title and Item Highlights provide together.