🧬 Protein Molecular Weight Calculator
Paste an amino acid sequence to estimate molecular weight (monoisotopic) excluding terminal modifications.
Non-letter characters are ignored. Only standard amino acids are supported.
How to Use This Calculator
Paste the amino acid sequence
Use single-letter amino acid codes without spaces or numbers.
Check residue count
Verify the calculator reports the expected number of residues.
Review molecular weight
Use the monoisotopic mass for mass spectrometry or protein characterization tasks.
Formula
MW = Σ (Residue Mass) − (Residue Count − 1) × 18.01056
Subtract water mass for each peptide bond formed. Terminal modifications (e.g., phosphorylation) must be added separately.
Full Description
Protein molecular weight calculations assist in designing SDS-PAGE, mass spectrometry experiments, and verifying gene translation predictions. The calculator uses monoisotopic residue masses for high-precision applications.
For average mass estimations, adjust the residue mass table accordingly or incorporate post-translational modifications manually.
Frequently Asked Questions
Does this include signal peptide removal?
No. Provide the mature sequence or subtract signal peptides manually.
Can I add PTMs?
Not directly. Add or subtract modification masses from the final result.
Why use monoisotopic masses?
Monoisotopic values provide higher accuracy for mass spectrometry compared to average masses.
What about ambiguous residues (B, Z, X)?
These are not supported. Replace with the correct residue or estimate separately.