Free lab tool
Peptide molarity & dilution calculator
Molarity equals mass divided by molecular weight and volume: M = mg ÷ (g/mol) ÷ mL. Enter any two of mass, volume and concentration with the molecular weight to solve for the third, then plan a dilution with C1V1 = C2V2.
Uses the formula weight you enter. For salt forms (acetate, TFA) use the salt's weight, and correct for net peptide content from the lot's certificate where it is reported.
Result
1.761 mM
2.5 mg/mL
Dilution calculator (C1V1 = C2V2)
Making a working solution from a concentrated stock? Enter the stock concentration, the concentration you need and the final volume.
Stock to take (V1)
1 mL
+ 9 mL diluent to reach 10 mL
The formula
Moles of solute are mass divided by molecular weight. Concentration in mol/L is moles divided by volume in litres. Because one milligram per millilitre equals one gram per litre, you can keep mass in mg and volume in mL: molarity (M) = mass (mg) ÷ molecular weight (g/mol) ÷ volume (mL).
Example: 5 mg of BPC-157 (1419.53 g/mol) in 2 mL gives 5 ÷ 1419.53 ÷ 2 = 0.00176 M, or 1.76 mM. The same solution is 2.5 mg/mL.
Questions
Frequently asked
Divide the mass in grams by the molecular weight in g/mol to get moles, then divide by the volume in litres. With mg and mL the units cancel: molarity (M) = mass (mg) ÷ molecular weight (g/mol) ÷ volume (mL). For example, 5 mg of a 1419.53 g/mol peptide in 2 mL is 1.76 mM.
Use the formula weight of the form you actually weighed. Lyophilised peptides are often acetate or trifluoroacetate salts, and the salt weighs more than the free peptide. The lot's Certificate of Analysis states the form.
Net peptide content is the share of the powder's weight that is the peptide itself, after counterions and residual water. HPLC purity does not measure it. Where a lot reports net peptide content, multiply the weighed mass by it before calculating molarity.
Diluting does not change the amount of solute, so stock concentration times stock volume equals final concentration times final volume. Solving for V1 gives the stock volume to take; top it up with diluent to the final volume. Both concentrations must be in the same unit.
mg/mL is a mass concentration and does not depend on the molecule. Molarity counts molecules: the same mg/mL gives a lower molarity for a heavier peptide. Receptor and binding assays are usually designed in molar units, so convert with the molecular weight.
Calculations run in your browser and are provided for laboratory planning. Check every result against your own records and the lot's Certificate of Analysis. All Neupeptides products are for laboratory research use only.