Metric scales have two parts:
Paper size (EG: @A1)
Scale factor (EG: 1:100)
About paper sizes
Every PDF also has a real world paper size, and because CAD mistakes are sometimes made when creating drawings, that real world paper size can occasionally be different from the paper size shown in the drawing’s title block.
If they are different, then the scale factor stated on the drawing will likely be incorrect, and because of this, it’s important to verify that both paper sizes are the same.
How can I verify a drawing’s paper size?
By clicking within the scale field on the “Measure” tab, Countfire will overlay a set of standard paper sizes so you can visually check the PDF’s real world paper size.
Once you know that, you can then compare it with the paper size detailed in the drawing’s title block.
If they’re the same (EG: in the above clip, they’re both A1), you can then move on to verifying the scale factor below.
If there’s a difference, you’ll need to adjust the scale factor accordingly.
About scale factors
Each drawing usually also has a scale factor detailed within its title block.
As with paper sizes, because CAD mistakes are sometimes made when creating drawings, this scale factor can occasionally be incorrect when compared with the actual scale factor of the drawing.
If it is incorrect then any measurements made using the scale factor detailed in the title block will be wrong, and because of this, it’s important to verify that both the scale factor in the drawing’s title block and the actual scale factor of the drawing, are the same.
How can I verify a drawing’s scale factor?
First, set the scale using the scale factor detailed in the drawing’s title block.
Then, add a “Scale Check” measurement to verify the scale factor is correct. For example, if you know that a doorway is usually about 850mm - 900mm wide, measure a doorway on the drawing to confirm this measurement.
If your drawing has them, grid lines or scale bars are good items to use to check the scale factor is correct.
Building grid lines
Whatever you use, it’s essential to check the scale factor is correct in each drawing, by verifying the resulting measurements against a measurement you know to be correct.
How to: Fix incorrect scales.