Hi, I've been trying to design a piece which will eventually be laser cut into perspex but I'm getting some odd things happening in the size of my design between devices.

One particular part of the design I've measured between two parallel paths and in Inkscape the measurement is 106.5mm.
When I save the SVG file and import it into GIMP, the same measurement comes out at 107mm.
Printed on plain paper from my crappy Epson printer, the measurement is 109mm.
Cut on card from a Roland cutter using the same file saved as an EPS, the measurement is 112mm.

It's driving me crazy because I've been doing all of my tests using printouts from my printer and the "last" step before laser cutting the perspex was getting the card cut, but it was off by a few millimetres so I'm unsure of the design being correct when it gets to the laser cutter.

Can anyone tell me what might be going wrong with my process here?

I've just printed it out at work on an HP Laserjet from Inkscape using the SVG file, and the measurement is 106.5mm, so something is working at least.