The Formula

Two public Amazon signals go in; one number comes out. The customer rating measures quality; the review count measures consensus — how many people are standing behind that rating.

The weights are not fixed: they shift with review volume, in three tiers. The fewer reviews exist, the more the star average has to say; once tens of thousands have weighed in, the crowd is the evidence.

The Three Phases

Each product is scored in exactly one phase, decided by its review count.

Quality Phase Under 1,000 reviews

Rating 50% Volume 50%

A handful of excellent reviews counts — but cannot carry the score. With thin data, the star average leads.

Volume signal saturates at 100 reviews.

Balanced Phase 1,000 – 10,000 reviews

Rating 30% Volume 70%

The crowd has spoken. Consensus now dominates, and a lone wave of early hype can no longer prop a product up.

Volume signal saturates at 1,000 reviews.

Consensus Phase Over 10,000 reviews

Rating 10% Volume 90%

At this scale the volume signal saturates at maximum. A 4.2★ across 25,000 reviews is what the world actually receives.

Volume signal saturates at 1,000 reviews.

Worked Examples

One product, one rating — three phases. The same 4.5☆ earns a higher score as consensus grows, while the star average itself matters less and less. Every value below is computed live by the same formula the rankings use.

Product Rating → Quality Reviews → Consensus Weights PM Score
Quality Phase 4.5★ 80 reviews 9.0/10 8.0/10 50/50 8.50
Balanced Phase 4.5★ 3,000 reviews 9.0/10 10.0/10 30/70 9.70
Consensus Phase 4.5★ 25,000 reviews 9.0/10 10.0/10 10/90 9.90

Why 8.5 → 9.7 → 9.9 for the same stars? Quality contributes 4.5, then 2.7, then 0.9 — as consensus firms up, the crowd’s verdict takes over the score.

This Product’s Score

Full arithmetic for CA-570 Adapter/Charger for Canon R60 ZR65MC ZR70MCDC10 DC100 DC19 DC20 DC21 LEGRIA HF G30 XA10 XA20 XA25 XC10 Canon EOS 5D EOS 40D EOS 50D Elura 60 Elura 65 Elura 70 Elura 80 Elura, recomputed live from current data.

5.0 PM Score
Quality Phase · Under 1,000 reviews HZQDLN · ASIN B07BK2GJ8C
Quality — customer rating 0.0★ → 0.0/10
Consensus — review volume 132 reviews → 10.0/10

0.0 × 0.5 + 10.0 × 0.5 = 5.00

View this product on Amazon

What We Never Score

Price never enters it

A $19 kettle and a $190 kettle face the identical rubric. Price is a purchase decision, not a quality signal — and Amazon prices move too fast to score against.

Only public signals

Both inputs — star rating and review count — come from Amazon’s own public data. Nothing proprietary, nothing self-reported by brands.

One formula for all

The same equation scores every product on the site, with no per-brand overrides, no manual boosts, and no exceptions — including the ones on this page.