AutoCAD scale factor: Setup

This is a very important topic when it comes to working on a project destined for either implementation or team-work.

When working on a project, it is necessary to select the scale at which you will eventually plot the drawing. You need to be able to draw while having in mind the relationship the object in real world and the object plotted on paper will have.

For real project, you should not just come up with some arbitrary scale based on what looks normal on whatever paper size you want to plot on. There exist a set of standard of Drawing Scale and Drawing Scale factor acceptable for the discipline you happen to work in.

CAD users use two different terms while talking about a drawing intended to be plotted: Drawing Scale and Drawing Scale Factor

What does scale factor mean?

A scale factor is simply a factor by which a drawing is scaled.

Drawing Scale VS. Drawing Scale factor

The Drawing Scale has been around since the beginning of technical drawing and on-paper graphic representation of objects. It existed long before CAD. Drawing Scale are expressed with / or : such as 1/2 or 1:100.

Let’s take this as an example: Drawing scale 1:10 simply means that 1 unit on the plotted drawing corresponds to 10 units in the real world.

The Drawing Scale factor is a single number that represents a multiplier. The Drawing Scale factor of a drawing is the conversion factor between a measurement on the plot and the measurement in the real world.

You can find in the following table some common Drawing scale and Drawing scale factor that you might make use of while working with AutoCAD

Drawing Scale and Scale factor

Drawing ScaleDrawing Scale FactorUses
1/16"192Large building plans
1/8"96Medium size building plans
1/4"48House plans
1/2"24Small building plans
1"12Details
1:200200Large building plans
1:100100Medium size building plans
1:5050House plans
1:2020Small building plans
1:1010Details

Having an opinion about the paper size is crucial to the Drawing scale you are using while designing.

Paper size

ANSI sizes

Sheet sizeDimensions in "Dimension in mm
ANSI A 8.5 × 11 216 × 279
ANSI B 11 × 17 279 × 432
ANSI C 17 × 22 432 × 559
ANSI D 22 × 34 559 × 864
ANSI E 34 × 44 864 × 1118

ISO sizes

Sheet sizeDimensions in mmDescriptions
ISO A0841x 1189Gives A1 when folded lengthwise into 2
ISO A1594 x 841Gives A2 when folded lengthwise into 2
ISO A2420 x 594Gives A3 when folded lengthwise into 2
ISO A3297 x 420Gives A4 when folded lengthwise into 2
ISO A4210 x 297

Architectural sizes

Sheet SizeDimensions in "
Architectural large E36 x 48
Architectural E30 x 48
Architectural D24 x 36
Architectural C18 x 24
Architectural B12 x 18
Architectural A9 x 12

The selection of a particular sheet size is based on the common practices in your industry. You have to narrow your choice based on the standard of your industry. If you know the desired sheet size and the drawing scale factor, you can calculate the available drawing area with zero hassle.

Reversely, if you know the sheet size and the world size of what you are going to draw, you can find the largest plot scale you can use. Simply divide the needed world drawing area’s length and width by the dimensions of the sheet.

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