Molecular Weight Calculator
- A web-based program that calculates the number of constituent atoms, molecular weight, and percent composition based on a molecular formula.
- http://www.humboldt1.com/~medusa/page/molecalc/

Molecular Weight Calculation
- Very simple web-based utility for finding the molecular mass, elemental composition, and degree of unsaturation given a chemical formula.
- http://www.chemie.fu-berlin.de/cgi-bin/molform

Molecular weight and elemental analysis calculator
- This unix program calculates the formula weight and the element distribution for a given chemical formula.
- http://www.st.hirosaki-u.ac.jp/~rmiya/xmolwt/xmolwt-e.html

McDalton
- Free formula mass calculator for Windows, uses the latest values of atomic weights as recommended by IUPAC. For educational purposes, shows calculations as well as the uncertainty of the result.
- http://hem.fyristorg.com/ch.s/mcdalton/

Formol
- Open source command-line molar weight calculator. C++ source code and Linux packages available.
- http://formol.sourceforge.net/

ChemCalc
- Online calculator for molecular formula, molecular weight, elemental composition, and isotopic distribution. Java recommended.
- http://www.chemcalc.org