Peptide molarity calculator.
Enter a mass and a molecular weight to get the amount of substance in micromoles and nanomoles, the molar concentration in any solution volume, and the mass that gives a target concentration. Pick a compound to fill in its molecular weight. Everything runs in your browser; nothing is sent anywhere.
Mass and molecular weight in, molarity out.
| Amount of substance | - |
|---|---|
| Molecules in that mass | - |
| Concentration in the volume | - |
| Mass for the target concentration | - |
The mass field means peptide, not powder. A lyophilized powder also holds counter-ions and water, so for an exact molarity start from the measured peptide content: see the net peptide content calculator.
Three lines of unit conversion.
Molarity is moles per litre. The amount of substance in a sample is its mass divided by its molecular weight: n = m / M. With mass in milligrams and molecular weight in grams per mole, the result is in millimoles, so the calculator multiplies by 1,000 to show micromoles.
Concentration divides that amount by the solution volume: c = n / V. Millimoles over litres gives millimolar; the tool converts millilitres to litres for you. The last line runs the same equation backwards: the mass that gives a target concentration is m = c × V × M.
Example: 5 mg of BPC-157 (1,419.5 g/mol) is 3.52 µmol. In 2 mL that is 1.76 mM, and a 1 mM solution of the same volume needs 2.84 mg. The molecule count comes from Avogadro's number, 6.022 × 1023 per mole.
Use the peptide's own value.
Every Helion compound page lists the molecular formula and weight, and the molecular weight calculator gives it for any sequence in one-letter code, including N-terminal acetyl and C-terminal amide caps. Published values from PubChem are the safest source; the CAS and PubChem guide shows how to find them.
Two things change the number. A different salt form (acetate, trifluoroacetate, hydrochloride) does not change the molecular weight of the peptide itself, but it does change how much of a powder is peptide. And a blend such as Wolverine is two compounds with two molecular weights, so each component gets its own calculation.
Why a label mass overstates molarity.
A lyophilized powder holds the peptide, its counter-ions and some bound water. The peptide content of synthetic peptides is often 70 to 90 percent of the powder by mass, and HPLC purity then tells you how much of that peptide is the target sequence rather than related impurities. A molarity worked from the gross mass on a label is therefore an upper bound.
For an exact value, start from a measured content figure: the net peptide content calculator turns gross mass, content and purity into milligrams of target peptide, which is the mass to enter here. The purity vs content guide and the TFA vs acetate guide explain the difference.
Five milligrams of each, in 2 mL.
| Compound | MW | 5 mg is | In 2 mL | 1 mM in 2 mL needs |
|---|---|---|---|---|
| BPC-157 | 1419.5 g/mol | 3.52 µmol | 1.76 mM | 2.84 mg |
| TB-500 (Ac-LKKTETQ) | 889.0 g/mol | 5.62 µmol | 2.81 mM | 1.78 mg |
| MOTS-c | 2174.6 g/mol | 2.3 µmol | 1.15 mM | 4.35 mg |
| GHK (no copper) | 340.4 g/mol | 14.7 µmol | 7.34 mM | 0.681 mg |
| CJC-1295, no DAC | 3367.9 g/mol | 1.48 µmol | 0.742 mM | 6.74 mg |
| Oxytocin | 1007.2 g/mol | 4.96 µmol | 2.48 mM | 2.01 mg |
| Kisspeptin-10 | 1302.4 g/mol | 3.84 µmol | 1.92 mM | 2.6 mg |
Molecular weights from PubChem, except CJC-1295 without DAC, which has no PubChem record and is calculated from its sequence. Oxytocin and kisspeptin-10 are reference compounds, not Helion products.
Start from the measured mass.
Helion's lab reports state the measured mass of peptide in the vial next to the labeled amount, along with HPLC purity and identity by mass spectrometry, so a molarity can start from the real figure. See the guide to reading a COA, the research library and the extinction coefficient calculator for checking a concentration by absorbance.
Specs and storage by compound.
Questions (6)
How do you calculate the molarity of a peptide?
Divide the mass by the molecular weight to get moles, then divide by the solution volume in litres. With milligrams and grams per mole the first step gives millimoles; divide by millilitres and multiply by 1,000 for millimolar.
How many micromoles are in 5 mg of a peptide?
Mass in mg divided by molecular weight in g/mol, times 1,000. For a 1,419.5 g/mol peptide, 5 mg is 3.52 micromoles.
What molecular weight should I use?
The peptide's own value from PubChem or the compound page, or the molecular weight calculator for a sequence in one-letter code. The salt form does not change it.
Does the calculator account for salts and water in the powder?
No. The mass field means peptide. A lyophilized powder also contains counter-ions and water, so use a measured peptide content figure for an exact molarity.
What is the difference between mM and µM?
One millimolar is 1,000 micromolar. Both are moles per litre scaled down; the calculator shows both.
Can I use it for a two-compound blend?
Yes, one component at a time. Each peptide in a blend has its own molecular weight, mass and molarity.
Published studies (3)
- Sequence-specific determination of protein and peptide concentrations by absorbance at 205 nm
- How to measure and predict the molar absorption coefficient of a protein
- Characterization of Synthetic Peptide Therapeutics Using Liquid Chromatography-Mass Spectrometry: Challenges, Solutions, Pitfalls, and Future Perspectives
Citations from PubMed for reference. They describe the compound in the literature, not any Helion lot, and nothing here is guidance on use.