I use rsvg-convert to convert SVG to PDF (works great, also with huge files).
SVG file is scalable and internally i use mm unit, so if document is 1200x1500 for me it is 1.2m wide and 1.5m long.
RSVG creates PDF document with paper size 423x529mm (if width/height args used 2400x3000 -> 846x1058), so there is some constant ~2.3868 i have to multiply width/height to get right paper size. But not exactly same fo X and Y, 1200/423 != 1500/529 (maybe i see paper size rounded to int).
What is this constant? I tried different DPI, but it seems, it is not related with this.
My convert command is simple
rsvg-convert -f pdf -o test.pdf test.svg