Peptide Molecular Weight Calculator

Welcome to GenScript’s online Peptide Chemical Formula and Molecular Weight Calculator. Use this free tool to calculate the chemical formula and molecular weight of your peptide of interest.

Calculate the Chemical Formula and the Molecular Weight of Your Peptide Now!

This online calculator determines the chemical formula and molecular weight of your peptide of interest. You can also specify post-translational modifications, such as N- and C- terminal modifications and positioning of disulfide bridges, to obtain more accurate outputs.

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.

  1. Please use the “single letter code” or the “multiple letter code” specified on our Amino Acid Code Table while inputting the amino acid sequence.

  2. Please use braces {} for three-letter entries; for example: AC{GLY}{ILE}{d-GLY}.

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

3. Indicate the position of any disulfide bridges.

  1. For example, an entry of ”5-12, 15-24” indicates the existence of a disulfide bridge between positions 5 and 12 as well as 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):