This is a comprehensive engineering unit converter with an intuitive spinning wheel interface. There is no add, no hidden code, no need for a network connection, and the total size is about half a megabyte.

Choose a category such as length, energy, entropy, electric charge, etc., from a list. The available units appear in two spinning wheels. Spin the wheels to select 'From Unit' and 'To Unit'. That is it. You can change the input value in the yellow field, sort units, or use the swap button. Additional info about a measure is displayed when the help button is pressed.