Online calculator for molecular formula, molecular weight, elemental composition, and isotopic distribution. Java recommended.

Open source command-line molar weight calculator. C++ source code and Linux packages available.

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.

Free software for Windows for the calculation of molecular weights. Also available in French.

This unix program calculates the formula weight and the element distribution for a given chemical formula.

Very simple web-based utility for finding the molecular mass, elemental composition, and degree of unsaturation given a chemical formula.

Calculate the molecular weight and percent composition.

A web-based program that calculates the number of constituent atoms, molecular weight, and percent composition based on a molecular formula.