# Thread: **HELP** Need help with scales

1. ## **HELP** Need help with scales

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I was working on a drawing today, i dont know the scale, there is a dimesion on there of 150mm i measured the gap in model space and it came out as 7.36 i want to make the drawing 1:1 scale in model space. what s the formula i need to work out the scale factor in which i need to times the drawing by to make it 1;1 in scale. So the dimension measures 150 rather than 7.36? Please help.

2. if you want it at 1:1

you could divide 150/7.36=20.3804

so if you scaled the drawing by 20.3804 it would measure 150 at 1:1 in model space

3. Not really a CAD-question but I do this things a lot (I get old drawings of houses and need to do dwg's of them) so this is what I do. The distance should be 150mm right? So divide 150 with 7.36 and you get 20,3804 (as in the real thing is 20,3804 times larger than the model)- then use SCALE and 20,3804 as the scale factor.

*hrmf* I'm always second with these things

4. I'm fairly certain it isn't necessary to do the calculations

Draw a line 150 long, beginning at one end of your supposedly 150 line

If you select SCALE, pick your objects, then type 'R' for 'relative', you should be able to just click to define the existing length, and effectively stretch the scale up to your required size - and it's more likely to come out more accurately

PS - you may need to fix the scale on your dimensions afterwards - whichever method you use

5. Originally Posted by Strix
I'm fairly certain it isn't necessary to do the calculations

Draw a line 150 long, beginning at one end of your supposedly 150 line

If you select SCALE, pick your objects, then type 'R' for 'relative', you should be able to just click to define the existing length, and effectively stretch the scale up to your required size - and it's more likely to come out more accurately

PS - you may need to fix the scale on your dimensions afterwards - whichever method you use

im going mad here trying this out when i select scale then my objects what do i use as the base point to scale from?

as i've tried several goes and dont seem to get anything to scale

Code:
```Specify base point:
Specify scale factor or [Copy/Reference] <1.0000>: r

Specify reference length <150.0000>:  Specify second point:
Specify new length or [Points] <150.0000>:

this is where i get stuck
Command:```

6. Identify the line you want to be 150 long - and draw a 150 line over it, or for ease of viewing draw a 150 circle centered on one end of your line

SCALE

select circle centre as basepoint (or common line end)

what does it say next? I've not got AutoCAD on this machine

7. oops, that'll teach me to read first

specify reference length should be - click one end of original line, click other end of original line

specify new length should be by clicking too

8. Hey Strix - you're a champ you know that right??

I've always wanted to use the Reference option in the Scale command (not a big fan of math...not a fan at all actually) but I've never gotten it to work - but following your lead it worked! Not that I know what the eff I did wrong before but anywho... Thanks

9. it's great for ROTATE too

I know I'm only a CAD monkey, but I've learnt some useful tips along the way - pleased to have been able to make one thing easier for you TRH

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Originally Posted by Strix
I'm fairly certain it isn't necessary to do the calculations ....

If you select SCALE, pick your objects, then type 'R' for 'relative', you should be able to just click to define the existing length, and effectively stretch the scale up to your required size
That's the way I use to proceed when I have to scale drawings with undefined scale. No need of calculator and precision is more accurate. (If you have a dimension of 150 reffered to a distance of 74.01542431 it is pretty boring to calculate and give a scale factor with 8 decimals)

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