# Measurement units in Blender?

I’m doing jewelery modeling for 3d printing. I know I can set the units in Blender from the generic Blender Unit to mm and such but what I really want to know is Blender’s circle curve settings “radius” the same as a real life ring’s diameter, the size of the ring hole where the finger inserts measured from one end to the other? OR do I have to convert the diameter size to radius size?

I want precision control of the ring size. Does it make sense?

I’m relatively new to this but as it’s been explained to me the measurement’s in Blender are arbitrary. They mean whatever you want them to. One unit could mean one millimeter for you and your jewelry or a half mile in a project involving maps. The point is you make something that follows the relative scale you decide on and then you determine how that translates to actual scale when you get around to 3D printing.

I know that doesn’t sound helpful on it’s own but it’s kind of like learning algebra and the fact that a letter can literally be any number. It’s an abstract concept. To help with that here are some links that are probably better for you than my explanations:

In my experience, the radius is just that - the radius, half the diameter.

A 3" diameter circle would require a 1.5" radius.

You can work in real world units indeed if you go to Properties->Scene->Units.
You can set the units to be metric. For small scales like milimeters you’d need to set the scale to .001 and blender will rescale accordingly.
And yes radius an diameter are NOT interchangeable terms in blender.

So everything in blender in regards to scale is based on radius? So in order to get the diameter I just need to times the raidus by 2.