Peptide reconstitution calculator

Calculate concentration and molarity

How the calculation works

Reconstitution is dissolving a lyophilized (freeze-dried) peptide in a measured volume of solvent. Three relationships cover everything the calculator does.

1. Concentration. concentration (mg/mL) = mass (mg) ÷ volume (mL)
2. Molarity. molarity (mol/L) = concentration (mg/mL) ÷ molecular weight (g/mol). Multiply by 1,000 for mM, or by 1,000,000 for µM.
3. Dilution. C1 × V1 = C2 × V2: the volume to take is the working concentration times the final volume, divided by the concentration you have.

A worked example. A 10 mg vial of BPC-157 (molecular weight 1419.5 g/mol) dissolved in 2 mL gives 10 ÷ 2 = 5 mg/mL. In molar terms that is 5 ÷ 1419.5 × 1,000 = 3.522 mM. To make 1 mL at 100 µM, take 28.39 µL of that solution and make it up to 1 mL with diluent.

Net peptide content: what the labelled mass means

The mass on a vial of lyophilized peptide is the gross mass of the powder. Besides the peptide itself, that powder holds counter-ions from purification (often trifluoroacetate or acetate) and a little residual water. The fraction that is peptide is the net peptide content, and it differs from lot to lot.

The calculator treats the labelled mass as peptide, which is the usual working assumption. Where an experiment depends on an exact concentration, correct for the net peptide content where it is known, or measure the concentration of the solution directly, for example by absorbance where the sequence allows it.

Molecular weights used by the calculator

Average molecular weights, checked against PubChem, for the peptides in our catalog that have a single defined structure. Blends are left out, because a mixture has no one molecular weight. The full chart, with formulas and CAS numbers, is on the peptide reference chart.

Get the printable reference chart

One page for the bench: molecular weight, formula and CAS number for every peptide above. Enter your email and we send the PDF.