Peptide Molecular Weight Calculator

How to use this peptide analytical tool

Simply type in, or copy and paste, peptide or protein fragment amino-acid sequence, including modifications, spacers, or special termini, and press the “Calculate” button.

The peptide molecular weight calculator will display average and monoisotopic mass of the molecule, as well as a table of mass divided by charge values, both in positive and negative scan modes, which is useful for mass spec analysis.

Take a look at the following posts for demonstration of what the calculator is capable of:

Peptide Properties Calculator User Guide

Amino Acids

Cyclic Peptides

Branched Peptides

For a quick sample of the output screen, you can load a random peptide from the list of peptides the analytical tool has calculated before. Please note: this is a rapidly changing project in development; look, feel, and functionality may and will change.

Example sequences

Linear peptide in one-letter code: KYICNSSCM

Linear peptide in three-letter code: Arg-Gly-Asp-Cys

Head-to-tail cyclic peptide: cyclo(GRGDSP)

Peptide with two disulfide bridges: [Cys2-Cys10,Cys4-Cys8] ACDC­RGDCFCG

Peptide with Biotin on N-terminal: Biotin-YGRKKRRQRRR

Peptide with disulfide bridge (1-6), capped at C-terminal (amide): Cyclic CYFQ­NCPRG-NH2

Peptide with isotopically labeled Valine and Isoleucine:

Peptide with Phosphoserine: Arg-Arg-Ala-Ser(PO3)-Pro-Val-Ala

Also on this site

Try the sequence splitter tool for fragmenting sequences of proteins and peptides with optional overlap.

Use the scrambler tool to randomly shuffle peptide or protein sequences.