How to Use This Calculator
Enter the peptide amount printed on the vial label and the purity percentage from the certificate of analysis (usually given as an HPLC purity figure). The calculator returns the actual active mass in the vial, then, if you enter a target dose, the adjusted amount needed to compensate for the peptide that isn’t pure active compound.
Why Purity Changes the Real Dose
A vial labeled 5 mg at 98% purity contains 4.9 mg of active peptide, a small difference at high purity, but the gap widens fast as purity drops. A 5 mg vial at 85% purity contains only 4.25 mg of active compound, meaning a dose calculated from the label alone would be about 15% short of the intended target. Certificates of analysis vary by supplier and even by batch, so checking the actual percentage rather than assuming a round number matters most with lower-purity or less established suppliers.
Where This Fits with Reconstitution
Purity affects the concentration calculation as much as the dose. Once the true active mass is known, the BAC Water Calculator works out how much bacteriostatic water to add for an accurate concentration, and the Peptide Molecular Weight Calculator is useful alongside it when converting between mass and molar amounts for research documentation.
Who Should Use This
Researchers working from a CoA that shows less than 100% purity; anyone keeping effective doses consistent across batches with different purity.
What This Calculator Does
The Peptide Purity Calculator shows how much pure peptide a vial actually contains at the purity stated on its certificate of analysis (CoA), and what dose you need to draw so the amount of pure peptide matches your target.
Formula Used
Actual pure peptide (mg) = Labeled amount (mg) × (Purity % ÷ 100)Adjusted dose (mcg) = Desired effective dose (mcg) ÷ (Purity % ÷ 100)Filler / impurity (%) = 100 − Purity %Example Calculation
Limitations
Only as accurate as the purity figure on the CoA, which usually reports peptide-related impurities by HPLC and not water or counter-ion content. It adjusts the dose, not the concentration; use the BAC Water Calculator for reconstitution volumes.
Frequently Asked Questions
How do I use a CoA to calculate peptide purity?
Find the HPLC purity percentage on the certificate of analysis, divide it by 100, and multiply the labeled amount by that number. For example, a 5 mg vial at 97% purity holds 5 x 0.97 = 4.85 mg of pure peptide.
What does HPLC purity mean on a peptide test?
HPLC purity is the share of the main peptide compared with other peptide-related impurities found in the test. It does not measure water or counter-ion content, so it is not the same as the total peptide content of the vial.
How do I calculate peptide content?
Peptide content is the share of the powder that is peptide rather than water or salts, and it is separate from purity. This calculator adjusts for HPLC purity only. If a CoA lists both, multiply the labeled amount by each percentage as a decimal, for example 5 mg x 0.97 x 0.80 = 3.88 mg.