OneConvert - OneConvert - fast online calculator and free file converter. Allows to convert different file formats and allows quick and accurate conversion between many units of measure.
Numi App - Numi is a beautiful text calculator for Mac.
iLovePDF - Free online PDF tool set
ConvertAll - A comprehensive unit conversion program.
Material Unit Converter - Quick, free, online unit converter that converts common units of measurement, along with 77 other converters covering an assortment of units.
Calculator++ - Calculator++ is an advanced, modern and easy to use scientific calculator.