Peptide Calculator

Welcome to GenScript′s online peptide calculator. Use this free peptide tool to calculate the chemical formula and molecular weight of your antigen or peptide.

peptide calculator quotation page

Use GenScript′s peptide molecular weight calculator to calculate any peptide chemical formula

This online peptide molecular weight calculator determines the chemical formula and molecular weight of your peptide of interest. You can include in your calculation post-translational modifications, such as N- and C-terminal modifications and positioning of disulfide bridges.

The peptide calculator is hosted on GenScript′s secure web server. Your data are protected using Verisign encryption technology. This service is available to the general public at no charge.


  1. Input your peptide's sequence data.  Please use only the two codes specified on our Amino Acid Code Table . Please use braces {} with three-letter entries, like so: AC{GLY}{ILE}{d-GLY}.

  2. Indicate what, if any, modifications have been made to the peptide.

  3. Indicate the locations of any disulfide bridges.  An entry of 5-12, 15-24 indicates on bridge between positions 5 and 12 and another between 15 and 24.


N-Terminal Modification:

C-Terminal Modification:

Other Modifications:
Abz/DNP    Abz/Tyr (3-NO2)    BSA (-COOH of C terminal)    BSA (-NH2 of N terminal)
BSA Conjugation on cysteine    DABCYL    DABCYL/Glu(EDANS)-NH2    EDANS/DABCYL
Glu(EDANS)-NH2    Head to tail Cyclic    KLH (-COOH of C terminal)    KLH (-NH2 of N terminal)
KLH Conjugation on cysteine    MCA/DNP    p-Nitroanilide    Succinylation    Tyr (3-NO2)
mini-PEG1    Cy3/Cy5    Cy2/Cy3    FAM/Cy3    FAM/Texas Red    FAM/Cy5    FITC/TRITC

Disulfide Bridge (Format: 5-12, 15-24):