Protein Fragment Molecular Weight Calculator
Paste a protein/peptide sequence or import a FASTA file. Select a subsequence either by highlighting directly in the sequence box or by entering start/end positions. All calculations happen entirely in your browser on your local machine.
Local processing only. This page uses plain JavaScript running in your browser. No sequence data is uploaded or sent to any third-party service.
Load sequence
Supported residue codes:
ACDEFGHIKLMNPQRSTVWY. Whitespace, line breaks, numbers, and FASTA headers are ignored. Unknown or non-standard letters are flagged.