Hello animators, this question maybe does'nt example to animation, but was wondering when you set the settings>preferences: to foot/meter/inches etc. how do you know how much space you are measuring.
example( if I have my settings set to foot/feet, and I'm building a plane how do I know if is 40 feet by 50 feet in diameter, and say building the walls how would I know or tell if one room has 12 foot high walls and another room has 10 foot high walls). If that does'nt explain, umm say I'm designing a room like mines and  the floor is 20 by 20 feet and the walls are ten feet by ten feet, how would I exact them dimensions? if anyone can help will be most thanked

the default units is centimeter, so if you create a cube of 1 1 1 unit, it is 1cm each. now if you change the unit to foot and create a cube of 1 1 1, the cube is much bigger because it's 1foot each.

After creating an object, if you modify it, it would be difficult to always be really precise, especially if you move vertices but it is still possible with the step move.

Anyway, usually in maya you create the more important reference in size and then you work with these. Also at the begining of a project if have to set the scale and units that you will use for the whole project. And if it is something that will be use for different project, make sure that you can easily scale it.

And as Fabis said, you have tools to measure, and they will give you the value in the unit you are working in.