Imperial to Decimal

From time to time, I come across drawings in the Imperial System.  Generally, these are on older projects or projects where I’ve collaborated with overseas design team members.  All my work is done in the Decimal System, so how do I convert these files suit my needs?  Well, it’s quite simple actually.

I’m going to use a very simple example, it’s a block of a standard door.  The first thing to do is open the file in DraftSight.

As you can see, it’s just a standard 3 Foot Door.

If I check the drawing units (click on the Manage tab, then select Units). You’ll see in our example, that our Units are set to Architectural.

The first step is to change the units from Architectural to Decimal and Units Scale to Millimeters.

Once you’ve done that, just click on Apply and then OK. You’ll be brought back to your drawing.

Now that your Drawing Units have been changed, you’ll need to scale up your drawing so the dimensions are correct. If I run the Distance command on the example, you’ll see that the distance comes out at 36 Millimetres.

Basically, after changing the units from Imperial to Decimal, 3 Feet (36 inches) has become 36 Millimetres. Obviously that’s not right, 36 Inches converts to 914.4 Millimetres. To correct this, we will use the Scale command.

Type Scale at the command line. You’ll be prompted to Specify Entities, just type All at the prompt and hit Enter twice. You’ll then be prompted to Specify Base Point, enter 0,0. Finally, you will be asked to Specify Scale Factor. To convert from Inches to Millimetres, your scale will be 25.4. Once you’ve completed the Scale, you’ll probably have to Zoom Extents to see your drawing. If I run the Distance command, you’ll see the distance is now 914.4 Millimetres.

Your Dimensions will still be in Feet and Inches. You’ll obviously need to correct this. You can either edit the existing Dimension Style (Dimstyle at the command prompt) or create a new Dimension Style and use the MatchProp command to change the Dimension Style.

And that is how to convert a drawing from Imperial to Decimal units in a few easy steps!

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MJ Smyth
The first time I used CAD, it was on a DOS PC with an 8088 processor, 640K of memory and a Hercules Mono Graphics Card... That, well that was a long long time ago. I switched to DraftSight the day it was released and haven't looked back!
MJ Smyth

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