Roundcorner measurement

I find myself struggeling alot, trying to figure out the radius of a rounded edge/corner of a part i may reproduce. So i made this measurement tool.
It has got edges for
- 1mm
- 2mm
- 3mm
- 4mm
- 5mm
- 10mm
- 15mm
- 20mm
- 25mm

Just hold it against the corner you want to figure out the radius of and read the number from the tool. Since Designspark Mechanical doesn't like paths/svgs or something like this, i had to do the numbers with roman numerals.