The droidConverter app is a free unit conversion, unit converter, utility (with ads) that allows you to convert many different types of units. It has a very simple interface that allows the user to select the type of conversion that they would like, for example Length. The user then would select the from unit (i.e. Feet) and the unit to which they would like to convert the value to, the to value (i.e. Miles).
PRO version does not have ads and has more conversions/calculators such as age calculator.