Toni & Guy Purple Shampoo 250mL

We don't rate products ourselves. We collect what each public rater already says, put every scale on common ground, and keep the disagreements visible instead of averaging them away.

1. 1

   Collect each rater's own score

   Every source keeps its native verdict for this product. We never invent a score for an axis a source didn't measure.

2. 2

   Normalize to 0–100, higher = better

   Raters use different scales: EWG's 1–10 where low means safe, Yuka's 0–100 where high means safe. We map them all onto one 0–100 axis and flip the ones that run backwards so the numbers are finally comparable.

3. 3

   Average per axis, but keep the spread

   Scores on the same axis become one representative number (their mean). When raters split by 20+ points we flag it and keep every rater's number. A disagreement is never blended into silence.

4. 4

   Your weights make the overall

   The ring is the weighted average of the four pillars using your weights. It's computed fresh every time and never stored, so there's no hidden “objective” default.