Free tool
Peptide content calculator
A lyophilised vial contains peptide plus water plus counter-ions. The peptide content figure on the certificate of analysis tells you how much of the powder is actually peptide — and therefore how far your real concentration sits from the one on the label.
What the vial and the COA say
The label mass is powder. The COA tells you how much of it is actually peptide.
Your answer
This is the figure to plan from when peptide mass matters.
Show the other figures
- Actual peptide in the vial
- — mg
- Difference from the label
- — mg
- Concentration if you assume the label
- — mg/mL
- Volume for one label-equivalent mg
- — mL
Arithmetic only. This tool converts between mass, volume and concentration for laboratory preparation and dilution planning. It is not dosing guidance, and nothing here is a therapeutic claim. All materials are supplied for in-vitro laboratory research use only.
How the arithmetic works
peptide mass = label mass × peptide content
This is the section of a certificate of analysis most often skipped, and the one that changes what you actually have. Purity and peptide content are different measurements answering different questions. Purity, by HPLC, tells you what proportion of the peptide present is the target sequence. Peptide content tells you what proportion of the powder is peptide at all.
A vial can be 99% pure and 78% peptide content at the same time, with no contradiction. The remaining 22% is water and counter-ions — usually trifluoroacetate carried over from purification. Where your work is planned in peptide mass rather than powder mass, calculate from the COA figure and not the label.
Frequently asked
What is peptide content?
The proportion of a lyophilised vial that is peptide, as opposed to residual water and counter-ions such as trifluoroacetate or acetate. It is stated on a complete certificate of analysis.
Is peptide content the same as purity?
No. Purity is the proportion of the peptide present that is the target sequence, measured by HPLC. Peptide content is the proportion of the powder that is peptide at all. A material can be 99% pure and 78% peptide content simultaneously.
What if the COA does not state peptide content?
Ask for it before ordering. Without it you cannot convert label mass to peptide mass, and any calculation planned in peptide terms carries an unknown error of typically 10 to 25 percent.