Last updated: April 13, 2026

Protein Molecular Weight Calculator

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Table of contents

Protein molecular weight from sequence

The molecular weight of a protein is calculated by summing the molecular weights of all amino acid residues and adding 18.02 Da for the water molecule from the N-terminus and C-terminus. Use one-letter amino acid codes (e.g., MTDGLNEKFKAL...).

Amino acid one-letter codes

A (Ala), R (Arg), N (Asn), D (Asp), C (Cys), E (Glu), Q (Gln), G (Gly), H (His), I (Ile), L (Leu), K (Lys), M (Met), F (Phe), P (Pro), S (Ser), T (Thr), W (Trp), Y (Tyr), V (Val)

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