Peptide Molecular Weight Calculator

Enter a peptide sequence using single-letter amino acid codes to instantly calculate molecular weight, molecular formula, and residue breakdown. Supports linear, cyclic, and C-terminal amide peptides.

Peptide type:
Molecular formula
Residue count

Residue breakdown

Quick load — common TitanForge research peptides

How it works: Molecular weight = sum of all amino acid residue MWs minus water (18.02 g/mol) lost per peptide bond. Linear: subtract (n-1) water molecules. Cyclic: subtract n water molecules. C-terminal amide: subtract (n-1) water molecules plus 1.008 Da for the amide modification. Non-standard amino acids (D-amino acids, Aib, modified residues) are not supported — enter the standard sequence and adjust manually.