Chris -

This is really tricky, since (a) the X axis scale isn't tied too strongly to
physical units, and (b) the bubble diameter isn't tied to any axis units.
(a) means that changing font size or the number of digits in the axis labels
will affect the X axis length, but you can tie it down using code related to
this:

http://peltiertech.com/Excel/Charts/SquareGrid.html

(b) is also tough, because you can specify a default maximum bubble size in
percent, where 100% is approximately 25% of the smaller of the plot area
inside height or width. This is the size of the largest bubble, regardless
of the order of magnitude of the bubble size values. You have to lock down
the axis scales first, as above, then determine a default bubble size, then
relate your desired bubble size to the input bubble size measurements. It
will require some trial and error.

An alternative that will give better precision of bubble sizes (without
improving in any way the precision of the axis scale) is to draw circles in
the worksheet, then use these as custom chart data markers:

http://peltiertech.com/Excel/ChartsH...omMarkers.html

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
http://PeltierTech.com
_______


"Chris" wrote in message
ups.com...
Hi,
I am trying to create a bubble chart that sets the radius/diameter of
the bubble so that it is on the same scale of as the x-axis.
I am overlaying these on maps and need the bubble to act as a radius
from a center point in km.

Thanks,
-Chris