Need help working out correct scaling.

[TravelingMan]

Hi there. This probably will sound like a real dumb question, but it’s really vexing me. 

I want to draw a 2d drawing of my dashboard in my motor home to scale. I want to be able to accurately place circles of the correct size for my instrument gauges so that I can redesign the whole board. 

I cannot work out how to correctly scale the drawing canvas, so I can draw a rectangle that will equal the real world size of 550mm wide by 290mm high, and then draw the guages, also to scale.  

The other alternative is using a different program. But as I only want 2d, then I thought Gimp was the best.

Hope that makes sense, and someone can assist me.

[Blighty]

Do File > New
Set the units to mm and width and height to 550 and 290
Set resolution to 300

Gimp works in pixels (not real world units like mm), so Gimp creates an image 6496x3425 pixels (see attached image).

[TravelingMan]

Thanks for that, simple when you know how. I will get on to it tomorrow.