# Thread: Scale conversion engineering drawings

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Originally Posted by ggunn
1" = 10' is 1:120 scale, isn't it?
yes
but they deal in feet
there are 2 scale types
engineers ":' 1:10 (1"=10'), 1:40, etc
architects ":' 1/4 (1/4"= 1'), 1/8, etc

2. Originally Posted by t_van
I'm trying to understand scales on engineering drawings.

I have a plan view drawing of a proposed electrical room on an 11''x17'' size sheet of paper. If the scale is marked 1/2"=1', is this the scale for the full-size drawing? What size paper is used for full-size drawings? How is the scale adjusted for 11"x17" paper?
Unfortunately, the size of the paper has nothing to do with the scale. Are you sure 11x17 is not the original intended size?

It's best not to guess any dimensions from a piece of paper that appears to be a reduced, full-size drawing. You can never tell how much it has been reduced. I recommend you get a copy of the architectural or structural drawing with some dimensions on it. ggunn has the best idea, but only as a last resort.

An engineering firm I know paid an "errors and omissions" charge when a designer tried to interpret the scale of a civil drawing by guessing the width of the parking stalls. The scale was off enough that the lighting calcs were wrong and more lights had to be added.

3. Here's what happens when the scales are mis-read.

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Originally Posted by K8MHZ
Here's what happens when the scales are mis-read.

classic

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## Scale conversion engineering drawings

Originally Posted by ggunn
1" = 10' is 1:120 scale, isn't it?
Yes, that is correct. That portion of my reply is an actual copy and past from an ANSI quotation.

Scaling is very confusing to many. The hardest part is measuring something on a drawing and converting that into real life dimensions. If the Drawing has anything that is dimensioned, carefully measure the dimension leaders then create a Multiplier to get the actual size.

Auto CAD allows the user to import a "Raster Image" (a picture or PDF). If there is something in that picture that is a standard size like a Dollar Bill, a Quarter, or even Coke can, you have a standard for that drawing and measurements can be created. AutoCAD can't Snap to a picture so the user needs to draw a line from one side of the picture object to the other, then an AutoCAD Dimension can be placed.
JimO

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Originally Posted by jimo144
Yes, that is correct. That portion of my reply is an actual copy and past from an ANSI quotation.

Scaling is very confusing to many. The hardest part is measuring something on a drawing and converting that into real life dimensions. If the Drawing has anything that is dimensioned, carefully measure the dimension leaders then create a Multiplier to get the actual size.

Auto CAD allows the user to import a "Raster Image" (a picture or PDF). If there is something in that picture that is a standard size like a Dollar Bill, a Quarter, or even Coke can, you have a standard for that drawing and measurements can be created. AutoCAD can't Snap to a picture so the user needs to draw a line from one side of the picture object to the other, then an AutoCAD Dimension can be placed.
JimO
But if you can get a pdf with accessible layers and a known scale, you can use the PDF Import feature to bring it into AutoCAD at scale. Also, any drawing that you do over the imported pdf will snap to its features if you want it to.

Imported bitmaps, e.g., rastered images, kinda suck; their features "fuzz up" when you zoom into them.