peptides with COA

Solution math

Purity-adjusted concentration

A vial labeled 5 mg at 98.6% purity holds 4.93 mg of actual peptide — which changes your true concentration. Enter the labeled mass, the purity figure from the Certificate of Analysis, and your water volume to see the effective content and real mg/mL.

Inputs

?mg on the vial
?% from the COA
?mL
Effective peptide content—
Labeled concentration—
True (purity-adjusted) concentration—
Shortfall vs label—

What this calculator does

A Certificate of Analysis reports a peptide's purity — the share of the vial that's actually the target compound. A vial labeled 5 mg at 98.6% purity holds only about 4.93 mg of real peptide; the rest is water, salts, or related impurities. This tool turns the label and the COA purity figure into the true peptide content and concentration, so your math reflects what's really in the vial.

How to use it

  1. Labeled massThe milligrams printed on the vial — the amount it's sold as, before purity is taken into account.
  2. Certified purityThe purity percentage from the Certificate of Analysis (for example 98.6%), usually shown next to "HPLC" on the COA.
  3. Bacteriostatic waterHow many millilitres of bacteriostatic water you're adding to dissolve the powder. ("Bacteriostatic" just means it contains a preservative that stops bacteria growing.)

Reading your results

  • Effective contentThe actual milligrams of target peptide in the vial — the label adjusted for purity.
  • Labeled conc.The strength you'd get if you assumed 100% purity (the optimistic number).
  • True conc.The real strength, based on effective content — what your draws should be based on.
  • ShortfallHow much less peptide you have than the label implies, in mg and %.

A worked example

A 5 mg vial at 98.6% purity, in 2 mL of water:

5 × 98.6 ÷ 100 = 4.93 mg real peptide

4.93 ÷ 2 = 2.465 mg/mL true concentration

vs 2.5 mg/mL assuming 100% — a 0.07 mg (1.4%) shortfall

Common questions

What does "purity" mean on a COA?

The percentage of the vial's contents that is the target peptide, usually measured by HPLC. The rest is water, salts, or related impurities.

Where do I find the purity figure?

On the Certificate of Analysis, typically labeled "Purity (HPLC)" — a number like 98.6%. No COA, no way to verify it.

Why does purity change my concentration?

Concentration is real peptide divided by liquid. If part of the labeled mass isn't peptide, the true concentration is lower than the label suggests.

The math, for the curious

Effective content. labeled (mg) × purity% ÷ 100

True concentration. effective (mg) ÷ water (mL)