InchMetric is an easy to use Inch to mm converter and vice versa.
The input method is extremely fast and requires only a minimum of keystrokes. To convert 12 3/8 inches to millimeters, just type:12Inch31/8
The result is computed immediately after every keystroke.
The result accuracy can be set from 1/2 inches to 1/128 inches and from 1mm to 0.001mm.