What the Peptigrity Purity Index measures
The index measures the recency-weighted average purity of research peptides that have been independently tested by third-party laboratories — currently 99.51 across the 11,433 HPLC results behind its 64 indexed compounds. It reflects the samples that were tested, not the market as a whole.
How the index is calculated
Each compound's index is the mean of its published HPLC purity results, weighted by recency: a test within 90 days counts at full weight, one within a year at 0.6, and older tests at 0.3. The composite is the test-count-weighted mean of those per-compound indices.
A compound is published only with at least 5 tests carrying a numeric purity. No single compound may exceed 15% of the composite weight, so a heavily tested compound cannot dominate the headline figure. The cap is enforced on every computation and currently binds on no compound: the largest contributor, Retatrutide, accounts for 11.51% of the weight. Blend vials and net-content-only tests are excluded from compound averages.
Three different totals appear on this page and each answers a different question. 11,433 is the number of tests behind the composite — the ones belonging to a compound that clears the 5-test threshold. 11,461 is the number behind the compound table, which adds the compounds still below that threshold. 13,153 is every published test carrying a purity value, including blend vials and certificates not attached to any compound row; it is the denominator for the purity-fail rate, never for the index.
Why a minimum of five tests is required
Five tests is the floor below which a single outlier moves the average more than the underlying quality does. A compound with one or two results — Adipotide, Tesofensine, Cortagen, Thymulin, IGF-1 DES, Follistatin-344, EPO (Erythropoietin), Humanin, Orforglipron, ACE-031, Thymosin Beta-4, Dihexa, Argireline — renders an em dash rather than a number, because a two-test “average” is a data point, not a measurement.
What counts as an acceptable purity level
95% is the research-grade purity bar and 98% is a strong result. Across all 13,153 published tests carrying a purity value, 0.27% fall below 95%, so most tested material clears the research-grade threshold — see peptide purity standards for the reasoning behind those cut-offs. Purity is also the less discriminating of the two failure modes: 7.27% of tests with a measured net-content figure are underdosed.
How the index differs from a vendor's own COA
A vendor's certificate reports one batch the vendor selected and paid to test; the index aggregates third-party results across many vendors and batches, with no vendor input into which samples are included. Because Peptigrity sells nothing and takes no vendor payment, no seller can influence the number that represents their compound.
Which laboratory produced a certificate matters as much as what it says. Every lab feeding this index is profiled on testing labs, and third-party peptide testing labs explains how they differ in method, turnaround and what they will and will not confirm.
Which compounds have enough data to be indexed
64 compounds currently meet the 5-test threshold, out of 77 with any published test. The full list, with each compound's index and 90-day change, is in the index by compound table above.
What the index does not measure
The index measures HPLC purity only. It does not measure endotoxin load, heavy-metal content, sterility, or batch-to-batch variance, and it is not a guarantee of any future batch. A high index means the tested samples were pure, not that every vial from every vendor will be.
How often the index updates
The index updates continuously as new certificates are submitted and approved; this page is regenerated hourly, and a nightly snapshot locks each day's figure so a citation dated to a given day stays reproducible. The date shown at the top is the newest published certificate, not the last time the page was rendered — it moves only when the underlying data does.
How to cite the index
The index is published under the Creative Commons Attribution 4.0 International licence — reuse it commercially or otherwise, provided Peptigrity is credited. Cite the composite with its date and sample size, and link to this page:
The Peptigrity Purity Index, Peptigrity, 2026-09-10. Composite 99.51 across 11,433 third-party HPLC tests in the index. https://peptigrity.com/purity-index