Introducing the Molecular Weight Calculator for Windows



Automated Installation

The latest version of the Molecular Weight Calculator for Windows is Version 6.49:
      Download the software from (5 MB, November 21, 2014)

International language files are included in version 6.x for English, Spanish, German, Portuguese, Russian, and Turkish.

VB.NET DLL Version

An open source VB.NET DLL version of the calculation routines used in the Molecular Weight Calculator is available at:

Changes in recent versions

Version 6.38 updates the mass of the most abundant isotope for each element used in the Isotopic Distribution calculator to match the monoisotopic masses of the elements

Version 6.37 extends the functionality of the batch calculation engine to support Isotopic Distribution calculations

Version 6.35 fixes a minor refresh bug on the mole/mass/dilution calculator form

Version 6.34 fixes a bug where I used hydrogen as the charge carrier mass rather than a proton. It also adds the ability to plot charge states > 1 on the Isotopic Distribution Modelling module

Version 6.32 fixes a bug on the capillary flow calculator that occurred when entering 0 for the particle diameter and finding back pressure

Version 6.31 includes a new window that allows one to compute the solvent viscosity for a water/acetontrile (MeCN) mixture using the Chen-Horvath equation

Version 6.30 includes an improvement of the graph that allows for editing of the frame color and frame style

Version 6.29 fixes a bug that caused versions 6.26 through 6.28 to crash on computers where the decimal point was defined as a comma rather than a period (common outside the US and the UK)

Version 6.28 adds the option to define a custom tick starting value and tick spacing for the X or Y axes on the graph component

Version 6.27 contains a minor bug fix in the Peptide Sequence Fragmentation Modelling module concerning the M+H to [M+nH]n+ conversion algorithm

Version 6.26 has undergone major code updates, including moving all of the primary computation routines to a Dll. It includes a greatly improved Peptide Fragmentation module (including the ability to have modified amino acid residues, for example phosphorylated residues), a highly configurable professional graphing component, improved abbreviation handling (including allowing abbreviations to reference other abbreviations), additional units in the Mole/Mass and Capillary converters, greatly expanded batch calculation options, the ability to subtract elements out of a formula (use the > symbol), and an updated Isotopic Distribution Modelling module which also now uses the new graphing component.

Version 6.22 contains a minor update to the plot window

Version 6.21 contains a new language: Catalan (aka Català), contributed by Antoni Escalas of Barcelona (Catalonia), Spain.

Version 6.20 contains minor bug fixes.

Version 6.19 adds the option to automatically display a desired module when the program is started.

Version 6.18 adds the ability to compute Isotopic Abundance distributions for any empirical formula, then plot the distributions for visualization (Screen Shot)

Version 6.16 adds the ability to submit a text file from the command line containing a list of compounds to compute the molecular weight of, or containing settings for running the Formula Finder routine in an automated fashion, writing the results to an output file.

Version 6.13 adds the ability to customize the 1 letter amino acid abbreviations.

Version 6.12 contains updates to the Lang_Russian.ini file and some minor bug fixes. Additionally, now allows formulas to start with a number or a dash.

Version 6.10 contains a new Peptide Sequence Fragmentation Modelling tool including ability to Plot (Graph) the ions, addition of inches for ID size on the Capillary Flow Calculator, and numerous bug fixes.

Version 6.06 contains a fix for a minor bug in the Mole/Mass/Dilution calculator.

Version 6.05 contains a fix to a Major bug in the Formula Finder that prevented users from changing values in some of the textboxes.

New in 6.04 is a Dilution calculator to assist in performing dilutions. It can also be used to estimate concentration changes when concentrating a sample via evaporation or sublimation.

Version 6.0 contains numerous improvements, foremost of which is new support for International Languages. Users may now edit a text file to translate all of the English phrases to any Roman or Cyrillic character-based language. The program also recognizes if the computer is set to use commas for decimal points rather than periods.

A utility to convert Amino Acid abbreviations between their 3 letter and 1 letter forms has been added. In addition, the maximum number of formulas that can be displayed simultaneously has been raised to 20 (though this is dependent on your current screen resolution).

View the complete revision history.


Screen Shots


The Complete List of Features and entire help file is available for browsing.


Other sites referencing the Molecular Weight Calculator program are:

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Last Modified December 21, 2020