Peptide calculators

What does the molecular-weight estimate include?

The estimate is the sum of average residue masses for the 20 standard amino acids, plus one water molecule for an unmodified linear chain. It is a sequence-based theoretical value, not a measured result from your material.

The calculator does not account for terminal modifications, cyclization, branching, nonstandard residues, counterions, residual water or isotope distribution. For those structures, use the appropriate structural calculation and confirm identity by the agreed analytical method. A matching theoretical value also does not establish purity or net peptide content.

How does the dilution calculation work?

C1V1 = C2V2 keeps the amount of solute constant when a stock is diluted. The three inputs must use consistent concentration and volume units. For example, preparing 5 mL at 2 mg/mL from a 10 mg/mL stock requires 1 mL of stock, followed by diluent to the specified final volume of 5 mL.

The result is arithmetic only. It does not verify solubility, stability, assay basis, losses during handling or suitability for a particular process. Use the batch COA and your approved procedure to determine the actual concentration basis and controls.

Which source values should you check first?

• For molecular weight, confirm the exact sequence and every terminal or side-chain modification before interpreting the estimate.
• For dilution, confirm whether the stock concentration refers to gross powder mass, net peptide content or another assay basis.
• For supplier comparison, keep HPLC purity, net content, water and counterion values separate rather than substituting one for another.

Read peptide content vs purity for the measurement distinction, or use the RFQ form to request the current specification and batch documents.