Here is how I use Inkscape to achieve precise measurements.

The following conversions are global definitions at the top of my Python scripts:

# measurement constants
in_to_px   = ( 90 / 1 )               #convert inches to pixels - 90px/in
cm_to_in = ( 1 / 2.5 )              #convert centimeters to inches - 1in/2.5cm
cm_to_px = ( 90 / 2.5 )            #convert centimeters to pixels

in_to_pt    = ( 72.72 / 1 )           #convert inches to printer's points - 72.72pt = 1in
cm_to_pt = ( 72.72 / 2.5 )        #convert centimeters to printer's points
border       = ( 3 * in_to_pt)       # 3" document borders

The client measurement data from the Inkscape extension is converted to printer's points.
('self.options' is how the Python script understands the input fields from the .inx extension file)

           # if customer's data is in centimeters
           if ( self.options.measureunit == 'cm'):
               conversion = cm_to_pt
           else:
               conversion = in_to_pt

           height                               = self.options.height * conversion
           chest                                 = self.options.chest * conversion
           chest_length               = self.options.chest_length * conversion
           waist                         = self.options.waist * conversion
           back_waist_length            = self.options.back_waist_length * conversion
           back_jacket_length           = self.options.back_jacket_length * conversion
           back_shoulder_width        = self.options.back_shoulder_width * conversion
           back_shoulder_length       = self.options.back_shoulder_length * conversion
           back_underarm_width        = self.options.back_underarm_width * conversion
           back_underarm_length       = self.options.back_underarm_length * conversion
           back_waist_to_hip_length   = self.options.back_waist_to_hip_length * conversion
           nape_to_vneck                    = self.options.nape_to_vneck * conversion
           sleeve_length                     = self.options.sleeve_length * conversion

           neck_width                         = (chest/16) + (2*cm_to_pt)     # 19th century patterns are very strange...

At the end of the script, the document is resized to the drawing, adding borders. The current script expects a maximum of 36" wide paper. It's possible to print to 8.5 x 11 letter paper and tape it together.

Inkscape displays a small part of the lower left document corner because this is a man-sized coat, but manual zoom is done with 'view/zoom/page' - no problem.

Save to .pdf regardless of zoom level, then send to the 36" wide printer.

- Susan