Full Scoring Methodology

Every ranked vendor receives a composite score from 0 to 100. The composite is a weighted sum of six category scores:

Each category score is itself a number from 0 to 100, built from weighted subscores within that category. The subsections below list every subscore, its point range, and what it measures. The subscore ranges within each category sum to 100, so the category score is simply the sum of its subscores.

A vendor must pass human review before any score is calculated. Vendors that fail basic standards for transparency, documentation, or community standing are excluded entirely and never receive a composite score.

The Value category deserves special attention because it is the category most often misunderstood. Value is not simply "who is cheapest." It measures whether the price you pay is justified by the testing behind the product.

The largest subscore within Value is the testing-to-price ratio (0-35 points). This subscore directly connects the Purity & Testing category to the price you pay. A vendor charging premium prices while running only HPLC purity earns a low ratio score because the testing investment does not justify the price. A vendor charging the same price while running a full QC panel — HPLC purity, LC-MS/MS identity, endotoxin, sterility, net peptide content, and conformity assessment — earns a high ratio score because the testing depth justifies the cost.

In other words, the best value vendor is not the one with the lowest price per milligram. It is the vendor whose testing investment is most visible in the product you receive, relative to what you pay for it. A cheap vendor with no COAs is not good value; a mid-priced vendor with comprehensive, current, batch-specific testing is.

Price competitiveness (0-40 points) assesses standing MSRP and price-per-milligram across the catalog. Because the score captures long-term pricing patterns rather than a single day's sale price, it may not always align with a simple side-by-side of today's prices. A vendor running a temporary deep discount is not necessarily a better value than one with consistently fair pricing year-round.

The remaining 25 points cover bulk and sale structure — whether discounts are transparent, consistent, and meaningful rather than opaque or misleading.

Zero COAs. A vendor with no certificates of analysis on file receives a Purity & Testing subscore of zero for COA Access, Testing Independence, Batch Integrity, and Verified Purity. It can still earn partial credit for Testing Breadth and COA Freshness only if the vendor provides credible public evidence of testing through other means (for example, a lab partnership announcement with a named independent laboratory). In practice, a vendor with zero COAs rarely passes the initial human review gate.

Score overrides. In rare cases, the editorial team applies a manual override to a vendor's composite score. This happens when verified data shows a significant change that the automated recalculation has not yet captured — for example, a vendor loses its primary testing laboratory and has not published a new COA in over 18 months, or a vendor is found to be reusing COAs across batches. Overrides are logged in the audit trail with a reason and are temporary until the next recalculation cycle.

Selection score floor. The Selection category has a floor mechanism. A vendor with at least 10 distinct peptide compounds in stock receives a minimum selection score of 40, even if stock consistency or specialty availability is limited. This prevents established vendors with solid catalogs from being penalized excessively for temporary out-of-stock situations.

Newly added vendors. Vendors that have been added to the rankings within the last 60 days are flagged as "newly added." Their scores are provisional and may adjust more frequently during the initial evaluation period as COAs, community feedback, and service data accumulate.

Suspended or under-review status.A vendor placed under review or suspended is removed from public rankings. Its score is preserved internally and reinstated if the review resolves in the vendor's favor. If the review results in exclusion, the score is archived.

When a new COA is added to a vendor's record, the Purity & Testing category is recalculated. The impact depends on what the new document changes:

• A new batch-specific COA with current date improves COA Freshness and Batch Integrity. If the purity percentage is higher than the previous document, Verified Purity may also increase. A single new COA can move a vendor's Purity & Testing score by 5-15 points depending on the baseline.
• A COA with new test types (for example, the first endotoxin or sterility test on file) improves Testing Breadth. Each additional distinct test type adds points up to the 10-point ceiling.
• A COA from a new, independent laboratory can improve Testing Independence if the previous testing was in-house or from an affiliated lab. This can move the subscore significantly if the previous score was low.
• A COA that replaces an older, undated document improves COA Freshness and may improve Batch Integrity if the new document is clearly lot-specific rather than a generic catalog certificate.

Because Purity & Testing carries 35% of the composite weight, a 10-point improvement in that category translates to a 3.5-point improvement in the composite score — enough to move a vendor up several rank positions in a competitive field.

Consider a hypothetical vendor with the following category scores:

The Purity & Testing score of 82 might come from: COA Access 16/20, Testing Independence 18/20, Batch Integrity 14/20, Verified Purity 17/20, Testing Breadth 9/10, COA Freshness 8/10. The Value score of 78 might come from: Price Competitiveness 30/40, Testing-to-Price Ratio 28/35, Bulk & Sale Structure 20/25 — reflecting a vendor whose mid-range pricing is well-supported by comprehensive testing.

If this vendor publishes a new batch-specific COA from an independent lab with 99.2% purity and an endotoxin test (a new test type), its Purity & Testing score might rise to 90. That 8-point increase moves the composite from 75.2 to 78.0 — a meaningful jump that could shift its rank position.

A composite score is a structured summary of verified evidence. It is not a guarantee that a specific order will meet your expectations. Scores reflect patterns across many data points — COAs, community feedback, service records — and a single transaction may diverge from the pattern. A vendor with a 90 composite score can still ship a delayed order; a vendor with a 70 can deliver a flawless experience.

Scores also cannot tell you whether a product is suitable for any particular use. Every product listed on this site is sold for research purposes only. A high purity score means the tested sample met a high standard under a stated method; it does not change the research-use-only status of the product.