With a sleek design aesthetic and a number of useful calculators, the MS iCalc app by AB SCIEX is an excellent iPhone app for mass spectroscopists. App users begin by entering a chemical formula to display properties of the compound such as mass and the number of rings/double bonds. (The periodic table-like keyboard makes entering chemical formulas slightly less painful.) From there, users can view the isotope pattern for that compound in either graphical or tabular form. Other features of the app include (among others) a calculator that calculates the mass/charge (m/z) values for user-specified peptide fragments; a table including the names, symbols, and masses of the amino acids; and a list of peptide modifications with their mass shifts. The only feature missing from this app is a help page.