Peptide solution calculator

Use this calculator to prepare peptide stock solutions in the lab. Enter the amount of lyophilized peptide in the vial and the volume of diluent you add to get the concentration; then work out how much stock to pipette for the amount your assay needs, or the molar concentration from the molecular weight on the certificate of analysis.

Concentration of a lyophilized peptide after adding diluent.

Peptide in vial mg Diluent added mL

—mg/mL

—µg/µL

—µg per 100 µL

For laboratory solution preparation only. Not for calculating doses for human or veterinary use.

How the calculation works

Concentration = peptide mass ÷ diluent volume. 10 mg in 2 mL gives 5 mg/mL, which is the same as 5 µg/µL.
Volume to pipette = amount needed ÷ stock concentration. 250 µg from a 5 mg/mL stock needs 50 µL.
Molarity = (mass ÷ molecular weight) ÷ volume. 5 mg of a 1,419.5 g/mol peptide in 1 mL is about 3.52 mM.

Tips for accurate solutions

Use the net peptide content from the certificate of analysis when it is given, not just the label weight.
Let the vial reach room temperature before opening, add diluent slowly down the side of the vial and swirl gently rather than shaking.
Label every aliquot with lot number, concentration and date, and store as described on the product page.