How our digital piano ratings work

Exact-listing evidence

We extract key count, key action and polyphony only when the exact listing states them with explicit wording. A similar model is not a substitute source. Semi-weighted action does not qualify as weighted or hammer action.

Specification and documentation components

Documented piano specification score = 100 × [0.40 × (88 keys explicitly stated) + 0.35 × (weighted or hammer action explicitly stated) + 0.25 × min(stated polyphony / 256, 1)], rounded to a whole number. Semi-weighted action does not count as weighted action. Key count and polyphony require their explicit units in the exact listing. These are documented equipment attributes, not measurements of touch, tone or learning progress.

Documentation completeness = 100 × [0.5 × min(feature bullets / 8, 1) + 0.3 × min(listing images / 5, 1) + 0.2 × (brand stated ? 1 : 0)], rounded to a whole number. This fallback measures source completeness, not instrument quality.

A documented key count selects the specification component; otherwise documentation completeness is used. Accessories receive no instrument score.

Customer review blend

Where Amazon publicly displays customer reviews for a listing (average star rating and review count captured from the public product page), the raw editorial score is 100 × [0.45 × (Amazon average / 5) × min(review count / 50, 1) + 0.35 × min(log10(1 + review count) / log10(1 + 5000), 1) + 0.20 × documentation score / 100]. The confidence factor min(review count / 50, 1) damps averages based on very few reviews, and the logarithmic volume term rewards large public review volumes, so widely and highly reviewed listings rank ahead of thinly reviewed ones. Listings with no captured public review data use the documentation score alone. This combined index reflects the public Amazon reputation and the listing documentation — it is not a physical test and not our own product testing.

The selected specification or documentation component is the base input to that blend. Comparators require a complete 88-key instrument plus a captured positive review count and valid average from its exact-ASIN public Amazon page. Weighted eligibility requires explicit weighted or hammer action; console and portable eligibility require the documented format. We retain one representative per model family within each shortlist, ranked by raw score then stable slug. The intent sets can overlap, because a portable piano can also have weighted keys.

Amazon may group reviews across variants and bundles. Captured counts describe what the exact-ASIN page displayed, not verified reviews exclusively about that configuration. Review scores and shortlist counts require a rebuild to change; they are not live feeds.

Displayed ratings

The displayed editorial rating is the raw blended score divided by 10, shown to one decimal on a 0-10 scale. There is no catalog normalization, rank interpolation, forced winner, forced floor or artificial gap. Equal scores remain equal: the available data does not justify a distinction. Ranking uses the unmodified raw score descending, then listing slug for exact ties; slug is a stable identifier, not a quality signal. The same raw score always has the same display rating in every shortlist. This is not a physical test result or an Amazon customer rating.

A raw score of 87 is displayed as 8.7 out of 10. This does not measure touch realism, listening quality or learning outcomes. We have performed no physical tests.

Freshness and structured data

Amazon prices, stock and approved product images are displayed only within their data lifetime, capped at 24 hours. Expired information is withheld, not guessed. Product pages use ItemPage with a Thing identifier, not Product offers or review markup. Informational sources are listed separately from exact product specifications.

Space planner

All inputs are inches: instrument width, instrument depth and your chosen bench allowance. Total depth is depth plus allowance. Area is width × total depth ÷ 144 square feet, rounded to one decimal, because 1 foot = 12 inches. This measures your chosen rectangle only, not ergonomic suitability or manufacturer clearance. See the space planner and planning guide.

Corrections

Email [email protected] with the page, ASIN and exact conflicting source phrase. Unverified claims remain unknown.