METHODOLOGY

Every number on PreCompare is either taken directly from a product’s Supplement Facts label or derived from it by the rules below. This page explains those rules so you can check our math.

Data sources

Product data (Supplement Facts rows, serving sizes, flavors, prices, and ratings) comes from manufacturer labels and retailer product pages. Every product is reviewed by hand before it is published. Prices and ratings are checked periodically, not in real time, so they may lag behind the retailer’s current numbers — always confirm on the retailer’s page before buying.

Unit normalization

Labels mix units (g, mg, mcg). We convert every ingredient amount to milligrams so products can be compared on one scale. Label rows are otherwise displayed exactly as printed.

Actual yields (the core idea)

Many ingredients are sold as compound forms that contain less of the active ingredient than the headline number suggests. Each known ingredient form in our database carries a yield factor— the fraction of the labeled amount that is the active ingredient itself. The “actual” amount is simply:

actual mg = labeled mg × yield factor

Example: citrulline malate 2:1 is roughly two parts citrulline to one part malic acid, so its yield factor is about 0.667 — a label reading 6,000 mg of citrulline malate 2:1 counts as roughly 4,000 mg of citrulline. A product listing 4,000 mg of pure L-citrulline (yield factor 1.0) therefore ties with it in our filters, even though its label number looks smaller. Yields are approximations of typical form composition, not lab measurements of any specific batch. Ingredient rows we cannot match to a known form are shown as printed and excluded from yield-based filtering rather than guessed at.

Price per scoop

Price per scoop = the lowest price across the retailers we track, divided by the manufacturer’s servings-per-container count. Where a label lists dual serving sizes (1 scoop / 2 scoops), we use the one-scoop serving.

Ratings

The star rating shown on a product card is the average of the ratings across the retailer listings we track for that product; each listing’s own rating and review count are shown on the product page. Ratings are collected from the retailers and are not our own assessment.

Flavor categories

Manufacturer flavor names (“Cherry Bomb”, “Blue Razz Freeze”) are grouped into broader categories so you can filter by taste family. The original manufacturer name is always shown on the product page.

What we don’t do

• We don’t rank products editorially — sorting is by the metrics above only.
• Affiliate commissions have no effect on inclusion, ordering, or computed numbers.
• We don’t evaluate whether ingredients or doses are effective; we only report and normalize what labels state.

Corrections

Spotted a wrong number? Tell us at aaronwoah@aol.com and we’ll fix it.