BraneStorm is currently in very early development.

From BraneStorm

Type:Length defines a dimension whose standard unit is m, corresponding to the metre Length unit in SI.

It supports the following units of measurement:

• 1 m, meter, meters, metre, metres
• 0.001 km, kilometer, kilometers, kilometre, kilometres
• 39.3700787 in, inch, inches, "
• 3.2808399 ft, feet, '
• 0.00062137119223733397 mi, ml, miles, mile
• 100 cm, centimeter, centimeters, centimetre, centimetres
• 1000000000000 pm, picometer, picometers, picometre, picometres
• 1.05702341e-16 ly, lightyears
• 0.004970 furlongs
• 6.68458134e-12 AU
• 1.43781452192667E-09 Rs
• 1.56786503817751E-07 Re
• 1.39875549842E-8 Rj

Feel free to add your own units.