Peptide molecular weight estimator
Adds up published average and monoisotopic residue masses plus one water for a sequence you type. It is an estimate for linear sequences made of the 20 standard amino acids. It does not say how, or whether, any material was made.
Result
Enter your numbers and choose Calculate.
Formulas
- Mass: sum of residue masses + one water (18.015 average, 18.0106 monoisotopic).
- N-terminal acetyl: + 42.0367 (average) / 42.0106 (monoisotopic).
- C-terminal amide: − 0.9847 / − 0.9840 relative to the free acid.
- Each disulfide bond: − 2.0159 / − 2.0157.
- m/z for charge z: (monoisotopic mass + z × 1.007276) ÷ z.
Estimate only. It cannot account for non-standard or D-amino acids, lipid or other attachments, cyclization other than the disulfide count you give, or salts and counter-ions. Compare with a measurement using mass spectrometry for peptide identity.
Residue masses are the standard published average and monoisotopic values. The tool gives a calculated mass for the sequence you type, which is a different thing from a measured mass and from a product specification.
Background reading
The arithmetic on this page is explained, with its assumptions, in these guides.
Guides
Glossary terms
Research use only. For laboratory research use only. Not for human or veterinary use. This page performs arithmetic on the numbers you enter and gives no recommendations about amounts. Check results against your own protocol and records. All laboratory tools · Laboratory guides · Glossary