How AutoCAD Interprets Units

when you make a drawing it is designed in some sort of linear measurement most of the world uses the metric system while other places like the United States use the imperial system of feet and inches.

AutoCAD doesn’t really know what those units are it only sees generic units drawing units are relative to AutoCAD it will only interpret the units when you go to print your drawing or when inserting other AutoCAD files or blocks it will translate your drawings units to fit the way you want to look on paper AutoCAD will take your line work and apply it to a scale factor when it prints it will take the size of the paper you are printing on and scale your drawing objects accordingly when you draw make sure to know what units you are using your units can be anything in fact they can be feet or they can be inches they can be meters and kilometers or even parsecs it doesn’t matter what does matter is that you drop to full scale or to real scale and you only draw in one unit there is a units setting in autocad where you can define or at least declare what your drawing units will be to do it just type in units on your command line
bring up your drawing units window here you will designate the type of units that blocks will be inserted in or other drawings it also sets up the way your units will be displayed while working in AutoCAD you can choose from your length or your angle settings and then your insertion scale the insertion scale is where you declare essentially the type of units you are using in this case this drawing is drawing in inches if you pick on the box you can see all of the different objects you have you can make it unitless which I suggest you never ever do it will just confuse AutoCAD and you especially when you go to print or to insert other AutoCAD files pick something commit to it so this file is set to inches you can also draw them as feet miles and millimeters centimeters meters kilometers micro inches mils yards angstroms and nanometers microns and decimetres decameters hecta meters and Giga meters an astronomical unit which is the distance from the earth to the Sun light years or even parsecs I think all I’ve ever done is inches feet millimeters to be quite honest
it will depend on your design genre and what you’re drawing and how you need it drawn this shows you how everything will be outputted or how it’s going to look when you draw
it’s simple enough and fairly
straightforward now your length type is up here this will define several different things you can choose from engineering scientific architectural or fractional or even decimal each one works a little bit differently the architectural and engineering display notations assuming that you are working in inches and it will display your units in feet and inches when you draw with either of these settings an object of a unit length of one will be one inch long a length of 12 units will be 12 inches long yeah 12 inches is the same as one foot but AutoCAD will only see it as being 12 inches it is smart enough though and can interpret 12 inches to be one foot and will display it as such it will display it as one foot – zero inches long
architectural format will display fractions of an inch in fractional form while the engineering setting displays them as decimals of an inch so an architectural format if I draw a line pick a point and I tell it to go 12:00 or 1:00
say one unit
direction
is one unit long
and to make it over 12 units as you can see AutoCAD is smart enough it tells me it’s one foot nine and thirteen sixteenths of an inch long
that’s how long it is I can change this display setting
switch from architectural to decimal when I select the object and see how big it is it tells me that it’s 21.8 to 372 units long which is 1 foot 9 inches etc so depending on how you want to work on what you’re doing if you need to work with inches and you need decimals maybe you’re working in a machine environment and you’re going to be machining surfaces that may be what you want to do but if you’re working as an architect you’re definitely going to want to use the architectural settings
typically a civil engineer will work in the decimals and typically if you’re working with the metric you’re going to want the decimal setting now switching from one unit type or insertion scale to another won’t change your line work it won’t automatically interpret this drawing as from going from inches to millimeters
it’s going to give you an error message this is still the same length
insert a block or two insert another CAD file from someone else it will just see the units as being metric and will automatically scale that object for me so you need to make sure that’s correct or else it will scale it and interpret it incorrectly
so that’s what you need to do here is to make sure this is set properly you know you also have angle settings they are the decimal degrees which we’ll use most often degrees minutes a second which if you’re a surveyor you might want to do that but they have a survey units which is very unique to a surveyor you have gradients and radians typically you’re going to use either the decimal degrees or the degrees minutes seconds a survey units look a little bit different they go with northing and easting units now you have your precision settings this is how precise that AutoCAD will display the length of your objects you can go to a half inch quarter inch eighth of an inch all the way down to one two hundred and fifty sixth of an inch if you’re in architectural form if you go to decimals it’s how many decimal places past the decimal that it’s going to be
otherwise it will just round up to any of these units so be careful depending on what you need to do and how you need to do it is where you need to set your precision to
the angles are the same way
I can go to as many degrees minutes seconds that I need to one of the problems with AutoCAD is that it can be so extremely precise you can draw much more precisely typically than what you can ever build so keep that in mind and just because that you can draw something in AutoCAD it doesn’t mean that you can build it that way

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