SVGSCALEFACTOR system variable
Svg Scale Factor
1 Drawing unit = X Svg pixels.
If set to zero, it will scale the current view to fit within the page size of SvgOutputWidth x SvgOutputHeight.
If set to a positive value, the SVG page size is calculated automatically to correspond to the required scale, when one drawing unit is equal to the specified number of SVG pixels.
E.g. 96dpi / 25.4 = 3.7795 - the corresponding scale factor for the conversion of 1 dwg unit into 1 mm Svg.