margin

type: double | point, default: <device-dependent>

If the margin is a single double, both margins are set equal to the given value.

Note that the margin is not part of the drawing but just empty space left around the drawing. The margin basically corresponds to a translation of drawing, as would be necessary to center a drawing on a page. Nothing is actually drawn in the margin. To actually extend the background of a drawing, see the pad attribute.

For clusters, margin specifies the space between the nodes in the cluster and the cluster bounding box. By default, this is 8 points.

For nodes, this attribute specifies space left around the node's label. By default, the value is 0.11,0.055.

graph {
  "1.5x0.5" [shape=rect margin="1.5,0.5"] # in inches
  "0.5x1.5" [shape=rect margin="0.5,1.5"] # in inches
  "1.5x1.5" [shape=rect margin="1.5"]     # in inches
}

graph {
    bgcolor=lightgray
    margin=0 # in inches
    
    subgraph cluster_one {
      margin=8 # in points
      a
      b
    }
    subgraph cluster_two {
      margin=16 # in points
      c
      d
    }
}

• Nodes
• Clusters
• Graphs

Search the Graphviz codebase for "margin"