The plotting window size can be found by using dev.size function and we can pass in for inches and cm for centimeters. For example, if we create a plot then we can use dev.size("in") to find the plot size in inches and dev.size("cm") to find the size in centimeters.
Consider the below vectors and create a point chart between those vectors −
x<-rnorm(10) y<-rnorm(10,500,35) plot(x,y)
Now finding the plotting window size −
dev.size("in") # in inches
 5.760417 5.750000
dev.size("cm") # in centimeters
 14.63146 14.60500
This will change if we drag the plotting window to right, left, upper or down side as shown below (dragging the plotting window to left) −
Now again finding the size −
 6.614583 5.750000
 16.80104 14.60500
This will not change until and unless we do not increase the plotting window manually.