This is a screen shot from the professional units conversion program "Uconeer" from Katmar Software. It is designed specifically for engineers and scientists. Click here to read the full program description.
When converting to fractional inches the precision can be set from 1/4 to 1/128 inch. Fractional inches can also be displayed as decimals. You can also choose to work in feet and inches, or inches only - for example a length can be expressed as 1 ft 6 inches or as 18 inches.
This converter will also convert SI and metric units of length (meter, cm, mm etc) to/from either decimal or fractional feet and inches.