Calculate the average isotopic mass of an unmodified polypeptide from its one-letter amino-acid sequence.
| Residues | – |
| Average mass (Da) | – |
Use this calculator as a clipboard check for an unmodified protein or peptide. Characters that are not standard one-letter amino-acid codes are stripped, then each remaining residue is added to the mass of terminal water (18.01528 Da).
The mass is the sum of average residue masses plus H₂O for the N- and C-termini. This is the average (chemical) mass, not the monoisotopic mass used in high-resolution mass spectrometry. Glycosylation, phosphorylation, disulfide bridges, N-terminal acetylation, and other post-translational modifications are not included.
Unknown letters after stripping (B, J, O, U, X, Z) produce an error; only A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y are accepted.
Amino-acid sequence: Paste the chain in one-letter code (ACDEFGHIKLMNPQRSTVWY). Spaces, digits, and other punctuation are ignored.
Residues: Number of amino acids counted after cleaning the sequence.
Average mass: Average molecular mass in daltons (Da).
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