How to set a fixed size for a shape

Question

I want to draw a circle of 4mm with minus sign inside it. I have set the m style:

\tikzstyle{m}=[circle, thin, draw=red, fill=red, minimum size=4mm]

however the minus sign extends the circle. I want the sign to almost fill the circle. I tried to change the line to be:

\tikzstyle{m}=[circle, thin, draw=red, fill=red, size=4mm]

but it didn't work.

How can I set the circle size to be fixed?

Answer 1

TikZ automatically adds separation between the text and the node border. When setting a minimum size for a node, it's usually a good idea to set inner sep=0pt:

\tikzstyle{m}=[circle, thin, draw=red, fill=red, minimum size=4mm,inner sep=0pt]